Agreed. Being a grunt on a set is incredibly difficult.
Someone here mentioned that video games aren't an industry that tends to afford much longevity. It's far, far worse for film. Again, go see how many movies the average boom mic tech works. Or any of the other people on the set.
Being treated like crap over 14 hour days on a job with virtually no upward mobility tends to burn a lot of people out. I'm sure some of you are nodding your head thinking that describes games, too, and it does to an extent (look at your QA testers), but the tenure for anyone else tends to be longer than Hollywood, and the jobs are easier to get.