Warcraft is actually fun to play even when you discount the in-game rewards system. It stays that way for much longer than most of its predecessors. Everyone I know that bought gold online for Warcraft did it for the fun of it, not in order to increase social status. This is in marked contrast to Everquest, where the items you had were a huge part of social status within the game.

Warcraft is not an especially social game as far as MMOs go. You are relatively free to play it in your own little bubble of friends. Competition is largely via PvP, which is almost entirely avoidable. This is unlike UO, which forced PVP, and unlke Everquest which forced intense competition for in-game resources.