Why are NBA players so skinny and are so lightweight?

I'm 5'9 190 pounds and I look up on profiles of NBA players and Kobe Bryant, Vince Carter, Tracy McGrady, Michael Jordan, Dominique Wilkins, etc. All these players are like 6'6, 6'7, some 6'8 and are weighing in at like 200 to 215 pounds at the most. I know Lebron James is heavy but that's really the average guy because of the other NBA players being so damn skinny. LOL