[Start Sarcasm] Because MMO`s are like girlfriends as soon as there is a new pretty girl on the block they leave the old faithful girlfriend (WOW) for the new girl on the block. Only to realize 3 months down the line that the new girlfriend is pretty much exactly the same as their first girlfriend (WOW) but just with a new pretty dress, so the leave the new girlfriend and go back to the old girlfriend till the next pretty girl shows up. [End Sarcasm]
MMO`s is a niche market catering for a niche group of people I dont like MMO`s purely for the fact that there is no instant gratification like when you play a single player game. Here it takes weeks and months to get to a level only to find that 1 million other people did exactly the same as you only better.