Well I will agree on everyone's opinion that tennis is very expensive. But why is it important for the lack of non-white ppl?

Are you implying that only white ppl are rich?

Why I'm not rich then!

I will agree with Dallas and Babble, tennis is simply more spread out to the white countries and its ex colonies.
Its pretty simple actually, here in Serbia and Montenegro you will see more and more kids on tennis court because of the success of Djokovic. But still you will see much more kids playing football or basketball because its much more cheaper.
In America, NBA is #1 or #2 sport league, and most of the black kids go to NBA or NFL. Its simple. Even Isner was a basketball player, Raonic etc... and how's tennis ranked in USA, I'm even wondering if its in top5 sports.
Every black kid born in America wants to be Jordan, James, Bryant, Wade and what not.. When that changes to Donald Young

, you'll have more black players in tennis..
So basically, here's your answer on the subject:
Tennis is a western European sport and has been exported throughout Europe and it's colonies