Because it would turn 30 Classes (10 classes, 3 specs each) into 60, making it even more complex to learn. Players would have to re-learn their specs, both in PvE and PvP, Mains and Alts. IF they choose to do only one. Should they opt for both, that's Two different specs to learn. Complicated and confusing for those who already play. And new ones? The game's complicated as it is. Make that triple if they aren't experienced with MMOs. I was when I first came into WoW, took me some while of getting adjusted with classes AND specs. My mother (yeah), after hearing me talk so much about it, and the news they would launch it here in Brazil, got very interested. I tried helping her through character creation, and it only got to a point where I said "Ok, forget almost everything I said, and pick whatever you think looks nice" because it is Too much to sink in as it is. My step-father, a hardcore console gamer (Yeah²) was listening, laughed and agreed, it's a lot of info to digest. To learn how to actually play the game ("Get a Damn Mouse Already"), move, attack, talk to others, PLUS what would become 60 different specs if they made PvE and PvP apart, some people like one or the other, some like both. Even if 1000000 people firmly believe this is best and wouldn't be that hard to learn, that's less than 10% of WoW Players, assuming it's around 11 millions.