In my experience, several things. First, in the US, it's an economic thing. Hockey in the US, in many areas, can cost a grand in league fees alone for a youth season. That is per player. A full set of equipment can easily run hundreds, and with growing kids, that is every other year. As much as it kills me, my kids don't play hockey because we can't afford it.
Second, at least among the black folks I know, there is no interest. Reasons such as lack of role models in hockey are often cited.
Third, of the black kids I did play with, they had a HARD time sometimes with racism on the ice. White kids, who would keep their mouth shut face to face, feel empowered with a mask, stick, and full equipment on to say anything on the ice. I heard things on the ice that would get the speaker killed in a parking lot, both in the Canada and in New England. I don't see why a black kid would want to subject themselves to that.