Gundam was awesome for this kinda stuff
Still one of my fav anime characters
Still one of my fav anime characters

With Gundam, I think they do it because it logically follows. It's set in a future society where the old national lines have been broken down in favour of even greater globalization, and the organizations we're dealing with are above global, so it makes sense to have just European or Japanese characters.
As it turns out, Japanese people are totally capable of thinking of ethnicity beyond their own and handling it in a sensible way, should that be what they want to do.