I fail to understand why you draw such a poor picture of a Maths / Physics PhD's life. Professors have a lot of interaction with students thus it is not exactly solitary confinement. Your picture of Academia is too dark.
I agree that there are people who get stuck in doing one Post-Doc after other and never get any tenure in life, surely it sucks for them but there are several Physicists and Mathematics PhD students who end up as a Quants on Wall Street and earn huge money.
If you read any posts / articles written by professors advising aspiring PhD students, you would rarely find them portraying a PhD life as fantasy filled life. So in my opinion Caution signs are already there.