That’s like asking why, if you’re a programmer why you don’t just work for another company on your day off. O

NBA players are professionals. They’re paid to play in the NBA season. They get plenty of tailored Xs and Os in their season and post season. They probably all need permission from their teams or stipulations on their contract that they can compete in the off season. If they get hurt, they (and their team) stand to lose millions of dollars.