I once heard a great description of the psychological profile of families at different income levels. Lower-income families tend to see money as a way to meet basic needs. Middle-income families see money as something to be saved for the future. And high-income families see money as something to be managed.
So what happens in basketball (or other professional sports for that matter, but the effect seems the most pronounced in basketball) is that you get these kids who come from low-income families who all of a sudden become millionaires. Yet to them, money is still just a way to meet basic needs, because that's all they've known growing up. Their definition of "basic needs" simply changes, and when their careers end they are left with nothing.
It's not really fair to expect someone who grows up in poverty to magically become a shrewd financial investor who knows how to manage exorbitant amounts of money. Hopefully they'll surround themselves with good people who can be trusted to advise them appropriately. But as we all know, that doesn't always happen either.
It's easy to pass judgment on these guys and say it's their own fault, but I think most people in their situation with their background would probably do the same thing. Hopefully the NBA or maybe the players union will start to take some accountability into advising these guys when they come into the league. But then again what 19 year-old with a $10 million contract is going to listen when someone tells them to start saving for their future?