Why do most of the people in urban areas who eschew the sidewalk seem to be African-Americans?

I see this very often. There’s a perfectly good sidewalk, and it’s as free of snow as the street is, yet the person walks in the middle of street. I keep on wondering why they do that. I don’t believe I have ever seen a white person do that, but if I have, they form a small minority of those who behave this way.

Is there a cultural reason to do this? Is it about safety? Does have something to do with racism? Is it an agressive act, slowing down the passage of white folks in their cars? This last doesn’t makes sense because it could just as easily be a black person in the car. Is it a protest against cars? An environmental thing? I’d love it if someone could explain this to me.