I'm black. I skied about 75 days last season, my first, at a range of resorts in Massachusetts, Vermont and New York, as well as Tremblant, Jackson Hole, Alta, Squaw Valley and all the western Washington resorts except White Pass (no pun intended). I saw one black couple in Jackson Hole and a black guy that I knew from college and later, work, at Alpental. Not one other black person. I think it is a function of exposure. Growing up, I became involved in alternative sports through exposure via some friends and some chance encounters with endurance athletes in high school and college, Patagonia catalogs and images on tv and magazines. I ended up road and mountain cycling, hiking, nordic skiing, etc. before taking up alpine skiing last season.
These are all non-mainstream sports and require introduction through a friend or family member. You just don't run into rally racing, base jumping or the like through mainstream media (at least not until Mountain Dew commercials and the 90's decade).
It really isn't socio-economic either. You'll find blacks in upper socio-economic strata gravitate towards sports like golf and tennis, the traditional "networking" sports in the business community. If your community does not have a historical network within your chosen profession (I went to school with lots of black first generation college students), it is important to make choices that provide access to existing networks. You're far better off playing golf than skiing.