I get to visit friends, and I can run and jump and do all the crap I can't do in real life vecause of my COPD
I'm chronically ill, it's quite severe, and I frequently have difficulty getting out into the real world. WoW is an excellent form of escapism, and it also helps me keep in contact with some of my friends.
I admit the false sense of accomplishment is nice, also the aesthetics of the game are a great attraction, and I do enjoy the lore.
I can do things here that I can never do in real life, and it's a nice little vacation from reality.
Friends. An escape from reality. Just more entertainment and use of brain power than watching TV or stalking facebook for 12 hours straight.
WoW is a highly polished mmorpg, no slight drag like with other such games, smooth game play...you can attain things in a reasonable amount of time, the levels are not ridiculiously drawn out, so you can have many alts. Its brain candy.
I play because public nudity isn't illegal in WoW, People in real life are too butthurt and sensitive about nudity.
I play WoW because it's the current best in the genre and will thus aid me in knowing what does and doesn't work when I am Lead Designer on my own MMO one day, or if one of my IRL friends and I manage to gain a majority hold on Blizzard's stock what could be changed for the better if they don't listen before then.
I play WoW because I just like being in the world. I don't know why, but I just like hanging out in Azeroth whether that's questing, dungeons or just helping forge some gear for random people. It's a nice escape from life for a while.