Youre looking at it from the wrong side. NCCAF is one of the largest making money leagues in the world and certainly the largest money making "amateur league" the reluctance is on the systems side, not the employee side.
It also provides the NFL with a no-cost developmental league.
I just wonder why there's not more clamoring to blow this rule up. I can't recall a peep since Maurice Clarett challenged it last.
I will say this, though - if we accept this rule (that you cannot enter the NFL directly out of high school) - colleges should at least be honest about this. The notion that you go and get a "Communications" degree (insert your alma mater's sports academics program of choice) is insulting to everyone involved. Why not make a "Sports" degree that focuses on the elements of being an athlete or former athlete? Why is that taboo?