Coming from a shoes-on culture I can give a couple points.
First, in the rare cases you describe (when was the last time you stepped on feces?) one would indeed leave their shoes outside. But in the day-to-day your shoes have some dust on them and that's it - you won't even notice it's there when compared to the dust that already accumulates daily. If you live in a climate where this assumption doesn't hold (snowy areas come to mind) then the equation changes.
Second, the floor is usually stone and therefore designed for being walked on with shoes. I would feel awkward walking on some polished wood, but if the difference between inside and outside is "this one is less coarse but just as hard" then I wouldn't see a good reason for taking my shoes off. I would probably avoid the rug, but that's me.
As for comfort, keeping your shoes on also means one less thing to do when going in and out. Do not underestimate the path with less friction.
I have seen in Switzerland that people leave their shoes at the entrance and switch to house shoes. Or they use a shoe cover when they enter house with shoes. Probably because houses are mostly wooden floored.
Between "Most of the west" and "Asian countries" it seems like it's the vast majority of industrialized countries that take off or swap their shoes inside. There's just an odd blip of over-represented online people who don't.
Try this , when was the last time you stepped somewhere that had previously been stepped on by someone who had walked on a spot which had been stepped on by someone who may have stepped on a spot trod on by ... go far enough back and it's all had feces on it to some small degree.
An easy way to keep this concept clear and understand the reasoning behind a 'leave the outside shoes out of the house' is something learned as a child.
Just like there is a Law of Conservation of Mass, and a Law of Conservation of Energy, and these two are the same law as defined by Einstein, there is also a Law of Conservation of Filth. The law may be stated as: "A spoonful of wine in a barrel of pigshit is a barrel of pigshit. A spoonful of pigshit in a barrel of wine is... a barrel of pigshit."
Taking off the outdoor shoes to come indoors changes the "is there trace amount of feces on my dining room tatami floor?" risk from "I cannot be reasonable sure," to "I can be reasonably sure that there is none." If guests find that too much friction to understand and accommodate, one might argue for a different set of guests who are less accepting of an allowable amount of pigshit in their wine.
I'm going to disagree with your law of "conservation of filth" on the grounds that it's pushing things too far. Whatever amount of feces comes into your system via walking downtown on a regular day and then bringing the shoes inside pales in comparison to the amount of fecal matter that enters via your toothbrush if you keep it in the bathroom. At some point a small amount of dirt is just fine, as evidenced by my immune system not even visibly reacting whenever I pick up and eat something that fell on the floor (as long as I follow the five-seconds rule). And people do go out to restaurants or, even worse, picnics, where all that separates their food from a much filthier surface is a piece of cloth.
I'm not going to say that every type of floor is to be walked on, with rugs and tatami mats being perfect counter-examples. But if a five-star restaurant doesn't ask me to take my shoes off (not evening Japan, AFAIK) then keeping them on is, from a sanitary point of view, probably okay.
The toothbrush analogy is weird, and untrue in most cases. And regardless, just one time stepping in crap, would make up for a lifetime of a few molecules hitting a brush at random intervals.
And of course, toothpaste is a cleaner, so it's not relevant.
But I find this all amusing, because wherever you take your shoes off? That's where all this supposed crap sits from all these shoes left outside. Which means you are walking in your socks in that area, after shoe removal, and entering the house.
So unless you levitate out of that area, your feet are still covered in this supposed crap.
The shoe rule in Japan stems from damaging floors. And checking your feet, shoes or not, is just prudent. But your feet or clean looking shoes?
The living area is usually elevated and so you can simply sit down, take off your shoes, and easily change into slippers that are ready at the edge of the living area. Or, one simply steps out your shoes (easy enough at least with sneakers) and to the living area. Easy to do unless one is infirm.
No, you actually step out of your shoes an up to a wooden platform which shoes never trod. And yes, the top and even many middle level dining establishments in Japan actually do require guests to leave their street shoes in an entry way, called a Genkan.
Nobody steps with their socks onto shoe trodden surface. It's not a complicated but of geometry, you loosen your foot in the shoes to make them ready for stepping out from, then step up onto a raised and dirt free platform, then if you have good manners, turn around, lower yourself, and use one hand to collect and turn your shoes so that they are not in the direct line of traffic and are facing away from the house, so that one may step into them from the wooden platform without needing to step backwards as you exit. This is amazingly simple, done by literally millions of people every single day, multiple times, and has been this way for centuries in all kinds of weather and many styles of shoes.
There is no dirt tracked in on your socks, there may be some 'stepping on the top of your own shoes' if you are in a rush and clumsy or a child. But grown ups rarely have much difficulty with this unless they are visiting from somewhere else and cannot be observant. Nearly every doorway in the country also has a handy long handled shoehorn to ease the donning of your shoes without requiring a seat. Community centers and elderly homes and some households with elderly residents will also have a small stool that is at an oblique angle between the 'dirty' shoe level and the clean wooden platform, allowing one to sit and take off shoes, then swivel without putting feet onto filth and stand again in the clean.
I'm frankly astonished at the seemingly purposeful denseness of comprehension for a simple act of cleanliness. The 'filth will make us stronger' approach reminds me of the historical writings of the 10th-century Arab diplomat Ahmad ibn Fadlan, who chronicled the Volga Vikings (Rus') and was the inspiration for the 'Viking morning bowl' scene from the movie The 13th Warrior. Just 'Ewww'
The toothbrush is a moot point if you have a separate be bathroom and toilet. If they are combined the spread of fecal particles is curbed by flushing the toilet with closed lid. And in the end the toothbrush is flushed before using and then coated with toothpaste, which often contains detergents and microbial agenda, and which is finally flushed out.
I don't think you can conclude from that incident that all soap is always contaminated. And even if it's not perfectly clean, in the end ist's all flushed away.
I don't really get what your point is. Are you regularly eating from the pedestrian way?
My point was that you seemed incredibly positive that Japan houses o'clean, and the rest of the world is as apes, in caves, picking parasites off of each others backs.
This obsession with shoes, doesn't cover the fly droppings, the dirt upon clothing, and the fact that your body is always covered in bacteria, your gut filled with bacteria, your lunch covered in it if you ever eat fresh greens, you will die without bacteria.
I'm not suggesting you walk around with dirty shoes, that's silly. Yet I feel you are a city dweller, because the world is made of dirt, and a rural farm worker spends all day in it.
To no harm to the worker.
Dirt is natural. Concrete is not.
So my point was just, you seemed a little upset at dirt.
I just don't get why you treat this as something super complicated. There is street and nature level dirt which contains an unknowable degree of contamination that can be unambiguously bad for you if you ingest it, no matter what that BBC article says, and the inside areas where people eat and sleep. The vast majority of cultures prefer to maintain that separation and to maintain a considerably higher level of cleanliness in the living areas, no matter if it's not at semiconductor fab level.
Specific to Japanese culture is just that they prefer to sit at low tables and to sleep on the ground on duvets; it should be easy to see why they want less dirt on the ground than other cultures.
naishoya was fairly damning of all other methods of living, so naturally I'll be quite overt in my response. And almost everyone was a farmer until the last 100+ years. The only way to generate enough food, without machinery, was for all to take part in its creation.
People were more used to having hands in dirt. That doesn't mean unclean, but I do find all city dwellers more "fussy" about dirt. They take traditions made for pragmatism (keep dirt off the floor, eg tidiness), and evolve it to fussiness(eg, contaminated).
Strange to make such assumptions about my perspectives.
I was simply explaining a foreign culture where removing shoes when coming indoors, and In confused that somehow my familiarity with these traditions is somehow indicative of my life experience or familiarity with microbes. Quite strange indeed. Lets clarify these assumptions.
In fact I was raised in a ranching and dairy household with over 600 head of beef at the dairy, and about 1600 head of beef at the ranch, each of which was owned or managed in various stages by my two grandfathers. Ihave previously lived for a few months less than a full decade in the middle of actual jungle in one of the rainiest locations on the planet without any infrastructure - literally a mile from the nearest paved road, and 3/4 of a mile from the closest vehicular access point with long periods of the year being closed off from that by high water on both sides. No power lines, no water lines, and out of the reach of cell service, so gasp, no internet!
During that time my wife and cared for over twenty goats and about a six pigs. We did all of our laundry by hand with a cranked wringer and buckets and lived principally off of what we could grow, harvest from the jungle, or milk from the goats and did nearly all of our cooking with self harvested wood, a mix of guava, eucalyptus, and mesquite/locust. In those years I have shoveled literally metric tons of goat manure out of sheds built from recycled building materials, one of which incorporated lumber from the shipping of mirror segments to the Keck telescope. < dakine when stay read dis, you know.
As for microbiome knowledge, I have made a living at times from my skills as a microbiologist. I have designed, built and used laminar flow hoods and sterile glove boxes for the isolation and identification of lambic brewing strains for award winning beer produced by two different local microbreweries, have prepared mushroom spore and tissue cultures in agar and liquid media, have cultured cheese and meat preserving lactic cultures (the dusty white wrapping on many different sausage varieties are examples of these lactic cultures) and to make cultures for lactic fermented pickles and kimchi intended as farmers markets and restaurant products with appropriate safety testing which has included sequencing, PCR and gel electrophoresis techniques. I routinely start sourdough cultures for home use and to share, and yesterday started a live ferment chili salsa that will be ready for probiotic consumption in about a week. I'm away from my home kitchen at the moment, but my kombucha polycultures are at a friends house, and my dry aged lactic cultured wild boar leg quarter is hangin at another friends farm awaiting my return.
I have also produced antifungal and antibacterial fungal metabolic products for veterinary use, and have collected, cultured, and sequenced coliform specimens from near shore runoff for submission to EPA wastewater monitoring as part of federally funded grant programs, having been the program designer and submitting author for those and other awarded STEM and educational grants. So, i am not unfamiliar with the beneficial aspects of microbiotic life forms and their importance to all functioning ecosystems and human life.
My Japanese culture experience includes 32 years ago years at rice farms and seaweed farms, and I am very familiar with the 'dirt' to which the common agriculture worker is exposed to in every day life. However, the differentials that I have personally observed include beef ranches in the US Southwest, Hawaiian beef and sheep ranches, and dairy operations in Japan is that the separation between the conditions in the barn and stockyard are more strenuously partitioned in Japan than elsewhere. It's not that I'm unfamiliar with 'muck', but that I was trying to explain that it is actually common and not very much effort at all for a culture, which has a strong tradition of separating their own dining space from the trough in the barn, to do so.
You are certainly free to convey whatever level of dirt you find reasonable into your own dining space, but please, don't feel that a high acceptance of dirt at mealtimes makes for a greater lifespan through immune system effects. The outdoors will provide all the challenge necessary for proper function without it being present inside the house.
But please, don't feel that I think people who wear outdoor shoes into their own kitchens are parasite ridden or otherwise uncouth, that image nor intent was never in any of my explanations of the how and why for Japanese shoe etiquette. Nor should you infer that I am dirt averse in general, only that I prefer not to have it on my own tatami mats or in my own house. The microbiome of the world is essential, but my personal preference is that dirt as well as cats and the rats they chase should remain outside of my own sleeping quarters.
As for fly droppings, the solution to those is to not allow an accumulation of the growing conditions for maggots to persist in close proximity to ones's indoors spaces, and to otherwise keep the screens on doors and windows closed. No flies will resolve to no fly shit, and a fly swatter plus a dilute peroxide\or\bleach dampened cloth will sanitize the mess for when they wander in from somewhere you cannot control, like the barn or an accidentally uncovered compost pile. Again, fly shit outdoors, no problem. On the walls, tables, and inside windows of my own home, nearly fully preventable and absolutely manageable.
I might type long expositions, but am in no way upset by making the choice to do so. Color me mildly dismayed when people have a hard time understanding that other people in other places do things in different ways, without any real difference in effort or loss of time as experienced by those other people, and upon hearing that those different traditions make a certain kind of logic and have a real benefit to those other people, become defensive as if they were being told 'your doing it wrong.' Not upset in the least, bemused and mildly dismayed in a slight measure.
The 'filth will make us stronger' approach reminds me of the historical writings of the 10th-century Arab diplomat Ahmad ibn Fadlan, who chronicled the Volga Vikings (Rus') and was the inspiration for the 'Viking morning bowl' scene from the movie The 13th Warrior.
Just 'Ewww'
Isn't it more that you spoke of "not doing it the Japanese way", and then referenced the comparator I've quoted?
Of what am I to infer, if we start at 'dirty shoes', and then evoked is this image?
While you may not be afraid of dirt, and you've provided context now, don't you think it's reasonable to make assessments, when someone connects my statements of "you're still going to track stuff in" and "a clean looking shoe is just as good as a foot", with the above?
So yes, it's reasonable to think one is over-concerned about cleanliness in such a case. And clearly from your response, you did not mean to evoke that impression.
Fine. No worries.
My comments about clothes and fly droppings, is that in rural environments flies abound. They land on you, and therefore deficate and urinate on you, and your clothes. Such is life. There was another poster worried about animal droppings in tree leaves and the grass, evoking concepts of the whole outside world being covered in animal leavings. Whether intentionally evoked or not, this is another source of my bafflement.
How much time have you spent in Japan? The bare foot never touches the genkan floor. It's alarming to do so.
Since you can't imagine it, you could consider looking up some videos of their use before mocking what you consider a fantastical impossibility. In fact it's so easy that children and the elderly succeed at it.
First, in the rare cases you describe (when was the last time you stepped on feces?) one would indeed leave their shoes outside. But in the day-to-day your shoes have some dust on them and that's it - you won't even notice it's there when compared to the dust that already accumulates daily. If you live in a climate where this assumption doesn't hold (snowy areas come to mind) then the equation changes.
Second, the floor is usually stone and therefore designed for being walked on with shoes. I would feel awkward walking on some polished wood, but if the difference between inside and outside is "this one is less coarse but just as hard" then I wouldn't see a good reason for taking my shoes off. I would probably avoid the rug, but that's me.
As for comfort, keeping your shoes on also means one less thing to do when going in and out. Do not underestimate the path with less friction.