Because there are too many really low skilled programmers who apply for mid- and senior-level positions. FizzBuzz is just a filter. We never asked FizzBuzz spec

Because there are too many really low skilled programmers who apply for mid- and senior-level positions. FizzBuzz is just a filter. We never asked FizzBuzz specifically at our interviews, but we asked to write a function to return a reversed a string. You wouldn't believe the amount of crazy that comes out of that one simple request. FizzBuzz is not a puzzle. It's a very straightforward question, there's nothing tricky about it. Your references are nice, but in many cases there's no easy way to verify that you wrote that code.