[Fomite]

Two notes:

1) I am evaluated on the progress of my students. While bad ones will actually be fired, good ones are more useful to me if they go off and get postdocs etc. Some of the most powerful "businesses" in the field are created by the network of people who all trained with the same PI and then went on to found their own labs.

2) A burnt out, trapped graduate student is not actually one that produces good work, in my experience.

3) Several grants, which are how I fund my lab, will look very poorly on trainees making no progress. There's very little exploitation that's worth a program officer at the NSF wondering if I'm worth there time.

Are there bad, exploitative PIs? Absolutely. But these people are assholes, not the only logical outcome of the system.