Because there's always a chunk of the player base that's never happy with anything.
Alliance players: It's not fair that Horde gets high elves, we have Alleria
Horde players: It's not fair that Alliance gets high elves, we have OG high elves
More generic: These aren't TRUE HIGH ELVES WAAAAAAH
It's an awesome move by Blizz tho, and I lowkey love that this expac is turning into the customization expansion.