They didn't, it's just an excuse for people that don't want arenas. One extremely pve-oriented dev said that he thought arenas were a mistake... and since then everyone on here and their grandmother has reposted that soundbite, completely out of context. He said the problem was that the game wasn't set up as an e-sport, and trying to turn it into one made balancing difficult. Obviously, he's talking about balancing PVE, as he was an extremely pve oriented dev, and didn't like that he had to balance around arena as well as raids.