As someone who does both a lot of interviewing (at Google) and gives a lot of advice on interviewing to people just starting out, this rhymes with my intuition about why some people get into interviews: even without the use of brainteasers (which, for the record, are not used at Google), the interview process is hard . People rarely come out of it without at least a twinge of frustration of humiliation. I'm not immun…
It's like military academy (or fraternity) hazing. You've been abused, therefore you want to pass the load of that abuse on. Maybe you delude yourself into calling it "tradition" or "high standards" or maybe you're just honest and enjoy the sadism of it all.
What did (or will) my successors do to deserve having an easier time than I did?
(Disclaimer: have not been to a military academy or a frat; but only to an undergrad school.)