My reasoning is simple, every single human noble house is white.
Proudmoore, Wrynn, greymane, trollbane, Menethil and so on
All white. If the PoC humans share the same lore as white humans.
Where are their noble Houses?
Do they not get any?
If yes then why not?
As for the multiple races, at some point the screen will run out of space with how many races we have or will have. Better for more organization but dont stop the cosmetic options train