[gradstudent]

I agree there are constraints on each possible outcome (we can't all be actors or astronauts) but I believe it is possible to do what you love in an intelligent way and still court success. If what your actors really love is film, there's plenty of ways to apply ones self to that pursuit without standing in front of a camera. The same is true for a PhD: even though not every graduate can get tenure many other alternatives exist.

Besides, I don't know what things are like in your neck of the woods, but around here, I don't know too many starving PhDs.

[pessimizer]

I know a bunch of underemployed ones with no health insurance.

[alxp]

Unions in Hollywood have made it so that an actor can get non-leading roles semi-regularly and still be able to make an OK living. The adjunct and post-doc system in academia is exploiting the hopes that an ever-shrinking pool of tenure track positions are still in your future so you should keep working away for less than you're worth to stay in the running.

Hollywood is still largely an exploitative, winner-take-all system but there are some built-in protections in the system to make it more sustainable. Academia seems to be on the verge of coming undone if they don't do something to keep the exploited class from revolting or just quitting en-masse.