Why do Dwayne Wade and LeBron James always get these flopping calls? Shouldn't refs know by now that they flop?

Refs know they flop but how can you ignore it if they time it right when their guard makes the wrong move. All they need is some semblance of a defense then they'll go for it. Pity the guard. It's a damn if they do, damn if they don't situation. I'd still put up with the defense if in any condition and try to get the offensive foul. That'll keep them quiet for a minute or two.