Title did not say it all.
Social district is the main place for customisation; which is one of the things that keeps me coming back to the game. It's also the main place to trade and just hang out for a bit and be, you know, sociable.
Populations thrive on community. If you don't give people a place to be sociable, you isolate them. Lacking space for downtime and AFKing leads to longer log-out times and subsequently, fewer people willing to boot the game up and hit the action and fight club districts.