I think the problem is that they think it will last forever. One example is Ryan Leaf. He was one of the top drafted QB's 10 or so years ago and I think he got a few million in a signing bonus. Turned out he didnt have what it takes and did not get his contract resigned. Last i heard he was breaking into homes stealing medication.
I really think that the NFL should have some sort of pension program (if they dont already) like you only get a % of your money and the rest is put into a trust for you and pays out like an annuity.
Ryan Leaf, for a while, appeared to be doing well. He made a huge amount of money, despite being a complete bust as a player. He still had much of that signing bonus and initial contract money years after "retiring."
Problem was, Ryan Leaf was also a first class idiot (which is one of the reasons he washed out of the NFL so quickly). Among his many failings was drug addiction.
The NFL does have a pension program, but it's not enough to keep idiots "living large." If they are used to spending millions per year, the NFL pension isn't going to help much once they lose their NFL (or NBA) income.
We all know the that the "scholar athlete" label is a JOKE for most of these clowns. They aren't in college to learn anything other than how to catch a football or throw a ball through a hoop. Since they aren't going to take serious classes anyway, why not replace their "underwater basket weaving" class with a class on money basics? Most, of course, will learn nothing from it, but if even a small percentage of them learn the basics, it might be worthwhile.