Again, how do you know that? Because they say so?
What makes you think that most of NBA players are not doing it simply because of all the money they can get? Especially the forwards and bigs. If you are 6'7" or taller and have a decent athleticism you are heavily pushed since the middle school/early high school to become an NBA player and make a bank - regardless of their interests and passions. The NBA history is riddled with so many examples of players like Amaechi, Bynum or Ayton who simply could not keep putting effort into basketball after they made their first millions - and it cost the a lot of money. And I am sure there are way, way more basketball players who manage to stick to the job routine despite disliking the job throughout their careers.