I played WoW quite solidly since vanilla right up until Lich King. the reasons that I was playing changed over the course of my career I belive.
When I first started it was just sheer enjoyment that kept me logging in. Seeing all this new stuff, areas, spells etc really wow'd me (pun intended) and I couldnt wait to log in again and see what else the game had to offer.
As time went on it was the raiding aspect that I enjoyed. Putting down new bosses after weeks of attempting with 40 other players on vent was a rush. Same through TBC my Guild was one of tne best on my realm so there was always the desire and competetive element to it.
Later I ended up just logging in for the social aspect of it, some of the people I was playing with i had now played with for years. I made some good friends and enjoyed the crack on vent way more than the actual game itself. The game just became a common denominator for me logging in to get a laugh with my online mates.
By the end I was just logging in out of loyalty to the guild as I was a senior member and didnt want to let the others down and probaly just habit. This was when i quit.
Looking back on it I cant actually belive I spent so much time on a game and dont think i ever will again.
well until SW:KotoR.............