My opinion is that it comes down to a cultural issue. It may not be the popular opinion among the politically correct people, and especially among those who get triggered by non-politically correct statements, but hey, to each his own.
Does a given culture promote self-betterment for the long term, or does it encourage eschewing future wellness in exchange for short term gain?
Until a given culture encourages the former, and discourages the latter, the "racial gap" isn't going to change.
I believe that a more accurate gauge of this would be looking at what happens to football players after their playing days are over. Did a particular player plan for the future, save up his money, invest his NFL earnings wisely, etc., or did he blow it on luxury cars, jewelry, mansions, hookers and blow, etc.? For that matter, seeing how freshly retired NFL players spend their severance pay (22K per credited season) might provide more insight as well. The pension for NFL players isn't exactly awe-inspiring, especially among those whose careers were cut short due to one reason or another.