It is not a hard argument to understand. Leaving school and a scholarship to pay for school before you get your degree is dangerous. At the very least you will have to pay for school when you come back which won't be so easy on your $60k salary. You also have no guarantee that you will get back in to the school (although for an athlete I am guessing it is likely that he will). Finally many, many players don't come back to school ever and often the ones that do are years later.

So is it possible to come back and get your degree? Of course. But to say you don't understand the argument is just silly.