Diablo 3 had an optional RMAH that was included for those of the player base who wanted to use it, they had the ability to use the regular AH as well. There was nothing in Diablo 3 that forced you to use RMAH, it was OPTIONAL. They incorporated it into the game, and may have somewhat built the game around it, but there was nothing implemented that ever FORCED the players to use it. Your assumption that WOW would force players to use it, is unfounded.