You make a good point, but it loses strength if the evidence shows most damage occurs during pro careers. I don't know if that's actually the case - I'm just pointing out that should be a relevant factor.
Second, playground leagues and high schools aren't making the money the NFL does. The difference in money is like the difference between me and Bill Gates. Greater, even. I wouldn't be opposed to the collegiate system chipping in commensurate with the money a particular program makes from football. But I say the ones making real money off this sport should be the ones paying the expenses.