We all identify with countless different affinities. Everything from the clothes we wear to the sports we play to the places we live to the people we hang out with define us in various ways, so it's natural for us to be passionate about them. GXC, as team-based social game, harnesses these loyalties and supercharges them into competitive play. Why conquer the world just for the fun of it, when instead you can show off how just much you like the Backstreet Boys, or your school, or your favorite character in a TV show?
Or maybe taking down your opponents is the best part for you. Schadenfreude isn't the most noble source of happiness, but we'd be lying if we didn't admit that some of the fun in any battle lies in totally crushing your adversaries. In some GXC games we've seen, the smaller teams gang up on the biggest team early on, just to watch the giant fall hard -- before taking out each other of course. In GoCrossPoliticalBash, the Clinton team was happy just to have outlasted Obama's team before being betrayed in their shaky alliance with Romney. And then of course there were the infamously straightforward strategic objectives of Harvard in the Ivy League Championship last fall: "Kill Yale." How gloriously honest, Harvard. :-P
Of course, watching the team you're most loyal to rise to epic success (or seeing your least favorite team crumble to the ground) is a lot better when you know your friends helped you along the way. One of the coolest features on GXC is the ability to recruit friends to stand strong in alliance with you on the field of battle. Granted, recruiting is beneficial just because you get more armies for each new player on the team, but it's also nice to have everyone in your dorm or major or school or office join up and band together in a giant unified force to take out the enemy.