Star players make it tough for the refs.
The NBA wants the star players to play, not sit, so there's pressure on the refs to look the other way sometimes when the star commits a foul. The refs can't call a foul every single time Wade uses his arms to clear space, which is technically an offensive foul. Wade does this on every possession he touches the ball.
The NBA wants its stars to get away with their technically-illegal stuff (e.g. LeBron's crab dribble, Rondo palming the ball constantly, KG doing all kinds of crazy stuff with his elbows and hands in the post) because it allows the stars to be more exciting.
Star players also tend to get hacked and bumped and pushed around and hard-fouled quite a lot, especially when they are physically dominant, like Dwight Howard or Blake Griffin. The refs can't call a foul every time this happens, but they surely know it happens. So there's pressure on them to give the star players a break now and then by not calling a foul when it goes the other way, or calling a foul that might seem ticky tack on its own.