[throw627357]

> I've always wondered why professors and supervisors, after experiencing these abuses themselves, continue to perpetuate them.

From their perspective, it's simply about the ends justifying the means.

You've learnt that relentless pressure and extreme demands, to an extent that elsewhere in society we would call highly abusive, produce results - they did for you, or you wouldn't be there.

This goes as far as rationalizing offensive personal insults as helpful tools - negative feedback can be very motivating to a driven person.

(That's not something I made up, I heard that point made nearly verbatim from a famous Max Planck director.)