Well that's odd, my quote button isn't appearing in this topic. Oh well. Anyways, at least in my case, I just grew out of MMOs. I put in a good 4 years or so with WoW, right up until the final content for Burning Crusade was released and, like I said, I just grew out of it. I could no longer justify paying the subscription fee to play a game that seemed much more like a job at that point than an actual game. Everything became one big routine. "Do dailies, do dailies, do dailies, raid night, do dailies, do dailies, raid night, rinse and repeat." Just the monotony of it all got to me, even all the boss fights were beginning to blurr together. Every boss fight was either a "watch your aggro" fight, a "deal with the adds" fight, a "special gimmick" fight (i.e. Shade of Aran in Karazhan in which you had to dodge the blizzard and such...god that was a LONG time ago), or just a straight-up beat-down.
When it all begins to feel like Raids are just a lottery in which you're hoping for a chance at having a chance of getting the item(s) you need, the game just gets exceedingly dull.
Do I personally HATE MMO's? No, I just feel that, like every other type of game, they're not meant to be played forever.