Why Are All The TV/Movie Heros White?

I just watched John Carter and watching a Canadian tv show Continuum. It got me thinking. Why is it still that all the heros are always white. The white man is always saving the natives. The black man is always the first to die or first in the movie or tv show to be committing a crime. There are generally no people of color in the future in Sci-fi movies and tv shows. Though you wonder how there are any Africans, Asians or brown people in the future since there is always only 1 or 2. How do they procreate with out any other people of their race around?