Since this is an RPG lore is required to create content. Blizzard can't just do something like:
Blizzard: "Hey guys, we created a new dungeon with some chickens to kill!"
Player: "Hell yeh, gonna fry some chickens with fireballs!!!
By the way, what have they done?"
Blizzard: "No reason, just go kill them for the loot!!!"
Player: "But shouldn't I have a reason to go kill so many?"
Blizzard: "Fine, the ate Malfurion Corn! Evil chickens!!!"
Player: "OK"
Remember, RPG isn't a FPS so you can't just give player a new map somewhere to defend some flag or destruct some buildings just for fun.