I didn't realize a person's ethnicity was automatically available when they post?
How do YOU know what race everyone is? Do you just assume everyone that posts is white unless they say otherwise?
That said, black americans have much more athletic role models than most white americans, and I would also say that in general lower-class people don't have the luxury of overcomplicating their hobbies (and black people, proportionally, make up a greater percentage of the lower-class in America, but you also see this with anyone that doesn't have much in the way of money or infinite access to computers and books).
When you don't have a lot, you don't want to wait around for results. Once these people identify what has worked for everyone else, they get on with it for the most part. People that live a very comfortable life can afford to shit around and try their best to avoid hard work in favor of finding a more "efficient" way to gain (which I have never seen pan out for anyone either).
But it isn't because they're "black" or "white".
Speaking from personal experience, I didn't stop overcomplicating things until I moved away from my parents and began living under the poverty line. When you have to cancel your home phone line so you can afford this chicken breast in front of you, you don't let that protein go to waste.
When I was 16-18 though, I thought I had all the time in world, and lived comfortably enough to never make real progress. A steak was just a steak. Now, a steak is an investment. Environment definitely matters as far as motivation goes, in my opinion.