[michaelt]

> why enter into an open-ended low-paid work contract with a professor with no definite end-date on when the PhD is granted?

This is less of a problem than you might imagine. While no school will guarantee to give you a degree regardless of your performance, it's pretty close. They don't offer the limited funded spots to anyone they don't think can make it.

The real compromises are that people go into their PhD thinking they're going to cure cancer and become a professor at Harvard, and come out of it having made a 5% improvement to a model for predicting the risk of one particular complication following treatment for one particular type of cancer, knowing that becoming a professor at Podunk College would take another decade of work. Or the decide to quit once they discover the reality of it.

The under-paid indefinite purgatory period is called the postdoc.