Because I hate dead, abandoned things in cyberspace, and because I actually like my erstwhile alliance-mates, I went away neat. I teleported my capitol to another state, filled in the hole with an NPC city, NPC'd my two secondary cities and then reset my account ... thereby wiping my capitol off the map.
Too much time, too much attention, and not enough fun. I'd spend two weeks on Evony morning and night -- building troops and "farming" NPC cities for food -- to build up an army that would last three hours when I went on the offensive. That's a very low work/reward ratio. Not to mention that executing an attack on an enemy city ... follows an invariable formula that depends on catching the player off-line, and getting the job done before his or her alliance-mates can send reinforcements.
...And it's not that I couldn't hack it. Over six months I deciphered the Evony mechanics sufficiently to give expert advice, and earn a rep as a highly aggressive and effective fighter. It just stopped being fun once the pleasure of discovery stopped coming.
So, after half a year of Evony immersion I'm done. Period. Stop.
Been there, done that. So long and thanks for all the fish.