I agree. I think that this will happen more over time. Part of this is academia protecting itself (or trying) from the hoi polloi, and part of it is institutional problems. If a 50 page book can teach a subject then the instructor isn’t needed right? More importantly, if pupils are using the book and a tutor, why have the professor?

OTOH, the professor may do research or bring prestige to the school, and as such the school tries to protect that professor. Likewise the book written by that professor may fund part of the research being done. There was a time when large monied interests would fund research, but that was transformed into government and mostly DOD funding during the Cold War… so Stanford, while producing many brilliant and visionary leaders of our time, also produced shit tons of nukes.

> If a 50 page book can teach a subject then the instructor isn’t needed right?

I honestly expect the opposite—it takes so much expertise to be able to condense so much knowledge in such short writing, with proper build-up of interdependent concepts and without losing clarity.

Most authors of textbooks are grad students who don't see a single dime out of it. If anything, I think that it is to reach the minimum word count to get it accepted.