Hello! I thought I'd weigh in here. I will even be unconventionally brief! (I cannot confirm this)
Like most people here I've quit wow - unsuccessfully - several times now. It always gets to that point where you just cannot be arsed to run another dungeon, fight another BG, gallivant around the same end zone, and then you realise that you're paying for that monotony. You quit.
Cue sense of relief, or reclaimed time, that feeling of "I don't need wow in my life", all that additional vitamin D you've produced from time outside. Awesome. Good for you! A month later you have a cursory look at the the forums, at a vid, the wow-eu forums if you're especially masochistic. More importantly you begin to look back with the delightfully rose-hued hindsight and remember all of the great times you had with guildies, and forget about everything else.
Next thing you know you've downloaded the client, subscribed - just for a month of course because, you know, it's temporary - and are running around with that old sense of enthusiam. "Oh, LFD, that's cool, that's novel, I like that. And changes to levelling as well - cross-realm zones, wow this is great!". But what's just arond that corner is the same old lack of gameplay interest that drove you away int he first instance.
So, my point at the end of the meander through my train of thought is that, WoW is WoW; it's the same as it's always been but occasionally gets spruced up and throws you a flirtatious wink at every expansion. The gameplay is, at its core, the same as it's always been. So what keeps pulling us back? The community. The social aspect. It always will because you cannot help but get closed to the mismatched band of internet chums you may never even have heard with own ears - or anyone else's ears! But you're attached to them nonetheless, and that's why we keep coming back. Well, that's why I keep coming back anyway.
P.S. Gnomes are awesome.
P.P.S. Pandas should be turned into a collection of patchwork slippers, gloves and bags for they clearly serve no other valid use. We can use dwarves for the leathery soles of said shoes for they are equally, if not more, useless. Could they not have at least just got a Scottish guy to do their voices?! Oh, or an actual cockney to do the worgen voices rather than some sort of Dick van Dyke abomination?! Basically I'm saying gnomes are the only thing the Alliance have going for them!
I reiterate: GNOMES ARE AWESOME.