The most maddening part of seeing companies throwing good candidates out along with the bad is that it's actively harmful for getting good candidates. You're doing more interviews, which means more opportunities for a bad candidate to somehow slip through your filter.

It's a principle-agent problem - having a strict filter gives the interviewer a way to deflect blame when they hire a bad candidate. This is at the expense of the company both through additional bad hires and through extra time and money spent interviewing.