I'm not even sure why he plays WoW, considering he doesn't even play any other games. He just started playing one day and never stopped.
I even tried weaning him off of it with some Super Meat Boy, but he put it down after a few minutes to "go raid with my clan," whatever that means.
I can lay it down for you like this. This is the thought process I subconsciously had, while playing and I'm sure many other players have.
"Oh man! Look at that spell i just got! Wow, it destroyed that boar! Oh, that spell looks even cooler! If I get that one, I'll be able to crush anything!" Repeat until level cap when it becomes either;
"Look at that item that just dropped! If I can get the rest of the set, I can move on to (insert more difficult dungeon here). And the bosses there drop this item set, which if i get all of them, I can then move on to (insert more difficult dungeon here)."
(While playing PvP)
"All I need is another (insert number) of honour from the battleground, then I can get this item, which will allow me to get even more
You don't have to know what the jargon means, but the general jist is that you level/raid/PvP so you can do it better.