at universities would have gotten fired from any private sector company they would work for. The evaluation process is just not near as rigid. Just take a look at how few professors are actually removed before tenure vs layoffs for the same type of position in the private sector. So if you are mediocre in your field you will find over time that a university position will earn you more money and be very attractive because of the benefits. Sure there are many excellent ones but the system isn't built to only allow those through. You have to play the game until that magic tenure button is pushed. And finally, for someone in my field (computer science) these professors are often earning big bucks on the side consulting, which is either not allowed for many private sector jobs or is almost impossible to find time to do.