The game has become more fun since the expansions came out, especially with cataclysm. Most people DO play because of the end game dungeons/raids and PvP, the only thing that made a difference in lich king was the new level cap (but you can get it so why should it matter) some new items from dungeons etc and the death knight which is extremely OP in PvP.
@Gum: I've been playing with a level 25 guild and two friends from rl and I've just hit 62 on my pally, it gets boring eventually until you start doing more PvP and shit. (even then all the twinks before level 65~ are ridic)
Also, made a death knight since I decided to try lich, level 58 in starting zone right now, waiting for friend to get on.