There's not a lot of high quality photo references available for other ethnicities. The most predominantly used reference site is 3d.sk, and 90% of their references are white europeans of various ages and body shapes. Add to that, the majority of vendors are going to create what they personally find attractive, and that's usually going to be their own race. So unless a vendor is willing, and financially capable of hiring their own models to use as reference, (which would not be feasible for most), they can only use what is most easily available. Plus, at least in N America and probably Europe, most of the top-rated movies and tv shows feature white people and always have, so that's going to be reflected in the trends of other areas as well. But all the daz figures contain ethnic morphs and its not difficult to spin a few dials if a character doesn't have the features you're looking for, then use them in combination with the appropriate skin texture. The first character I made for V4 when she first came out was an African girl, so I know its possible with the morphs that are included. 

 

~Shane