I agree with pjmlp, it's become a substitute for actually interviewing/evaluating the candidate. Especially if they are trying to hire for something they don't already have, it's a form of bikeshedding. For example, if they need a database expert because the team has been faking it until this point, they can either learn how to hire one, or they can focus on brain teasers and "culture fit", and feel good that whether or not the person is expert, they passed the test.