I wouldn't say it's that. The West Indies has some of the most passionate players/fans in the sport.
My guess is that it stems back to South Africa's apartheid roots, and while the policy might be gone, there is still a sense of the white community having a "head start" over the majority of black dwellings.
I think the main issue is opportunity, which should be the main focus. Excellent talent can be found even in the poorest of communities, the question is, if the opportunity never arises, does this talent ever go anywhere? Quotas are merely a way of forcing the outcome without having to put the effort in to solve the cause.
Well I only really meant the black people of South Africa and like I mentioned football is dominated by black players there so it could well be that any aspiring young black athletes there would just rather play that than cricket.
But yeah investment in poorer communities should be the way to go here. Especially for young school kids and what not, get them playing more sports like cricket and not only will that encourage the development of those that like it but it will also grow the sports popularity, it's kind of hard to like a sport if you've never even played it. Giving black kids better opportunities to develop as well as encouraging more black kids in general to try out and participate in the sport would work. It would take a fair bit of time and investment, but in the long term it should be well worth it.