When you send them a proof or an exercise and you do poorly they more often than not berate you until you understand what a fucking brainlet you are.
I've always found this comforting since even if I get pissed and shit, it always ends up helping to fine tune my work, people in humanities have trated this valuable experience for half hearted constructive criticism that doesn't hit hard enough to make a change. Each and every time a professor has called me out on my bullshit has made me a better mathematician.