I shamelessly admit it here. I love when content goes on farm. I was ecstatic as Firelands went from hard to easy. I love feeling my gear improve, seeing my DPS or health go up, looking at my avoidance and mitigation and realizing that yes, I actually can get passive unhittable just through gear. (I'll miss that when the two-roll combat system comes out.) I like going back, months down the road, and tearing Baleroc in half like wet tissue paper. Remember me?
Part of this is simply because I like WoW best when I'm killing stuff. I don't like to sit idle in Stormwind or Orgrimmar, and I'm not terribly moved to stand around hawking my crafting wares or playing the Auction House. These are fine activities, to be sure, but they're most certainly not what I like to do in the game. No, the reason I played seven years ago is the reason I play now, because I like to hit things in the face with the largest possible things I can.
And taking their stuff -- I mustn't forget how much I like taking their stuff.