I'm honestly curious about this myself as FF has always given off a feel of "we all are in this together". Not to say that individuals can't have their skirmishes, or FC vs FC skirmishes for example but I'd like to know storywise in the grand storyline why would pvp even make sense if we are all fighting against the same evils.
A good FFXIV lore site: http://ffxiv.gamerescape.com/wiki/Eorzea