Having to actually form a group and walk to the dungeon makes it exclusive for a big part of the playerbase because all they know is the "wait for random queue in town" WoW. Most people playing WoW today is so lazy they just want to be able to get everything with as little effort put in as possible, and if they can't get that they need to make it very loud and clear on forums by crying instead of actually trying to do something in the game.