Who have nothing better to do but spend their money. There's also rumors that a team is a good way to funnel money.
I've been told most arenas are sold out depending on size. Plus it's rare chance to see some of the American basketball stars.
There are roster rules where I think only two americans per team, so some players will get dual citizenship to be added to a certain team. Problem with that is that some of these same countries will then require you to play on the National team.