A side effect of the Alliance core being the "default Fantasy good guy" races. It's difficult to think of meaningful variations - Dark Iron are literally an evil clan made ally.
And Human subraces are a scandal waiting to happen - for other races, you can just have "the same, but in another (darker) skin color". You can see how that's not an option for Humans.
Instead, other Human races have to be significantly different in other ways - we got ones that were afflicted with a werewolf curse, and now stockier ones that presumably had some Vrykul blood reintroduced into their line. Which reminds me, some Alliance players are so un-imaginative that they would have preferred Kul'tirans to just be "the Human model, but with other class options & racials and of course that cool coat from the Heritage Armor".