Treating someone like crap during the interview process makes them think they can treat others like crap once they get hired.
Stop being a jerk when trying to hire people
Andy Boyle

This fully captures the inception of the problem. Often, a single person (asshole) introduces a tactic like this into a company’s hiring practices and it takes hold as a cultural rite of passage over time. Eventually the justification for continuing it is an instinct or a reflex… “They made ME do it when I interviewed so why should these new candidates get a free pass?”. Agree wholeheartedly with the conclusion that the jerk in the interviewer’s chair will continue to be the jerk in the manager’s chair once you start the job.