Because the interview process is structured to "raise the bar" but is also highly random. As with any tech company, you have to run the gauntlet to get a hire.

Because the interview process is structured to "raise the bar" but is also highly random. As with any tech company, you have to run the gauntlet to get a hire. It's politically easier to have candidates reinterview when they fail rather than get permission from executives to "lower the bar."