I have talked to a few Neil, most of them like the way they cook, and they aren't inclined to spending the money and effort to produce food for someone else that they might not like. I think in the neighborhood I grew up in, most of the folks didn't have the money for the tools, much less the travel and meat for cooking competitions. Now, a lot has happened since I left Richmond, and there are many folks of color, not just blacks, but, all colors, that do have the wherewithal to compete, I can't comment about them.
Although, I do have a theory, it has to do with two components of the equation. One is that many of my friends families saw BBQ as a social event, or a church event, that was meant to be spent with family and friends, enjoying the compnay, not making it into a sport, or work, but rather meant to be a leisure activity.
Others that I have known that tried it didn't much care for how the BBQ was judged, they knew the product they wanted to produce and had no intention of changing it to fit other folks ideals of good BBQ. That being said, it is dangerous to take any of this as speaking for an entire race of folks.
I will say, that with a few exceptions, in the Chinese and Japanese communities, when you talk about cooking ribs for 6 hours, or brisket for 12 hours, they look at you strange. I think there are just a small handful of us who spend the time. None of my family or friends think it makes any sense what I do. In a sense, this refers to an overarching comment about our individual cultures and what we have come to expect from cooking food. I think BBQ competition has a root in certain cultural traditions and not others.