The thing is, if they were to implement PVP servers, then we would see threads of "WORLD PVP IS DEAD! BLIZZ-I MEAN SE KILLED WORLD PVP" when the fact is usually that the majority of players just don't care for pvp.

And we all know that "world pvp" is code for "ganking that level 7 Warlock with your level 100 Rogue".