I get that. A lot of the time it really does boil down to luck. You either are in the right place and time to make important contacts or you're not. Some people have the personality to hold on to those contacts and some people are not built like that. And after years of grinding, with some good years and some sparse years, the lure of regular employment with a pension and health plan that you can get from teaching starts sounding pretty good to them and their family. Stability.
Working in the film biz is like running away and joining the circus. It's great when you're young but wears on you when you're older.
.However, I don't think they should let someone teach film unless they've actually worked in the biz and wrestled around in the mud.