The xp is definitely a draw but I think that strat is pretty interesting in itself.
Having competitive, organized battles is a nice change of pace and reminds me a little of reenactments in that people actually follow orders to form shield walls, timed charges/retreats, a legitimate forward line, etc. The use of siege gear is another element that makes it better for roleplaying, with the exception of gigantic ladder teepees. It's also much more balanced in the sense that players fighting for the same faction all have access to the same equipment so you can't really buy your way into performing better like you can by outfitting yourself in all +3s and cutting down peasants on the battle server. There's an interesting kind of anonymity too since everyone's using supplied gear and they're harder to recognize, like sometimes you'll go to run down some lone guy and find that he's way more skilled than you anticipated.
Of course there are also downsides to this kind of competitive organized play, like not being able to play when you're inebriated or low level. Not to mention having to listen to people nerdrage when they're losing a battle.
