Plenty of junk science, including a thesis I decided not to publish, while my advisor wanted the extra points on his resume. Many PHD students are stuck because they got a hard stem degree (like physics) but realized that job pickings were a little slim without further academic development. Or they are foreigners and cannot stay in the U.S. without studying.
Passion does not always last forever. Especially when you got off-ivy league schools. Didnt you hear stories in school about graduate students who were simply stuck for a decade because of lack of interest from them and/or their advisor? Not totally farfetched.