Perhaps I should have worded my statement differently - it's not that the players deliberately didn't challenge themselves, it was more that they were "encouraged" to focus on football. Especially in big time high school and college programs where there's just too much money and prestige involved for anyone to rock the boat or, god forbid take anything off the main focus of football.
For some players, too, they know the allure of the NFL can outweigh anything else, especially if they can run like the wind and ain't too smart but come from a really poor background. The school might know football is their best way out. Sad but true.