Amateurism itself is a class-based concept. In Walter Camp's day, an amateur was merely a generalist who didn't specialize in a particular sport or hobby. This excluded members of the "working classes," because their specialty in physical labor gave them an unfair advantage over gentlemen of the privileged classes (like Camp). The idea of paying amateur athletes was unnecessary, as their social position made it unnecessary.
By the early 20th century, academics transformed amateurism into a moral code consistent with collectivist principles. Howard Savage, a Carnegie Foundation official in the 1930s, said "professionalism in school and college athletics … is a most serious evil," and that amateurism represented "the moral struggle between force and the uses to which, with the sanction of our civilization, it may be used and should be put." In other words, athletes were barbarians who had to be tamed by the "civilizing" presence of academics. Savage noted that while it was acceptable for students in artistic fields to profit from their work – because they offered "tests of even temper and self-control" – it was never acceptable for athletes to profit from their efforts...
Of course, there is nothing wrong with the universities profiting from the athletes.
It's worth reading the whole thing.
hat tip: http://williamlanderson.blogspot.com