What happens is as follows. People come into the profession, very often young and pretty inexperienced, and they are persuaded, coerced, manipulated and bullied by their management to work extremely long hours. After a while a large proportion drop out, for obvious reasons. Those that remain have the stamina and the will, and they move into more senior positions where they themselves become the persuaders, coercers, manipulators and bullies of the next cohort of newly qualifieds. And so ad infinitum.
It's obviously, as you say, a very good system for the employers, particularly in schools. Especially given that by many measures the quality of educational outcomes is improving.