Players are recruited based on their height. The taller the more likely they are recruited. Some of these tall basketball players never dribbled a ball in their life but are scouted by the NBA on first glance whereas there are average to short people that have been playing basketball all their life and have the passion and enjoyment of playing it. To have height divisions of basketball would allow these height challenged players to fulfill their dreams. Plus if you have only giant basketballs, how are short fans supposed to relate to them?
Lots of the fame the NBA got was because of the number of different guys, big or small, got together to play a good professional game of basketball. Spud Webb had created a great slam dunk contest game versus Dominique Wilkins. Would we have seen that if there were divisions? Probably not, the height difference makes very creative moments. Remember Magic Johnson playing center? That was one of the best moment in sports history, that is what makes basketball fun.
That's why you play certain positions. In boxing or wrestling you don't have positions. So if the other team has a 6'8 guy then I'm going t put my tallest guy on the 6'8 guy and try to shut him down. This isn't a sport about trying to be fair with everyone. If this sport was fair then it wouldn't be any fun to watch.
If a 5'9 basketball player were to play with a another player that was 5'2 would it be a fair game? Wouldn't the taller basketball player have more of an advantage? It would make much more sense for players close to the same height/weight to play together. If I had to wrestle someone heavier, taller and stronger than me, who would have the advantage?