Unknown why they are so biased. But when you think about it and realize humans excel so much at everything. (arcane, holy, frost magic) and the only excuse for this is because humans aren't immortal so they are more strong willed than elves who are immortal and live a very young life.
So what about all the other races that aren't immortal or grow a thousand years old like Orcs, Trolls, Dwarves, Gnomes, etc. Where is their potential?
It's just so fucking god damn stupid that the best priest out there is Anduin, best mage is khadgar and Jaina, best warlock atm is that one fel dude that's the leader of the black harvest. Best paladin is Turalyon.
It's all just humans. Wouldn't be surprised if suddenly Kul tiran shamans and druids creeped up on the other races with their power level succeeding Orcish shamanism or Night Elven druidism.
Even on dating hot elven babes humans exceed lol.
Blizzard you're so god damn boring and awful that you can't write other races.