I'd say it comes from playing to have fun. The majority of play isn't going to be a "sword"-measuring contest, and by helping people out, you too might also benefit. Part of the aspects of MMO gaming, which is especially true with the crowd that came from FFXI, is that these games are a social game as well as a "Fight Spell Item Run" RPG. Anyone can(and often does) claim to be the best tank/dd/healer on their server, but are they all playing the same way? Probably not. What makes the difference among these claims to the average person? By making connections, teaching others, and even making a habit with requests, your own world grows, the game becomes that much more expansive, that much more enjoyable.
