I read an article about this in When Saturday Comes a few years ago. Apparently Asian families don't encourage their children into football because it isn't seen as a respectful profession (cricket is, rugby isn't, and so on). And despite the potential rewards, it's a big risk to go for football, and so the children are dissuaded from attempting.
That's why there are so few who come through the academy systems; Zesh Rehman, Michael Chopra, and the Nabi brothers pretty much the only exceptions.