Many things, MMO's, the ability to feel connected, reliance on people other than yourself.
Hey, wanna go ass to ass with me using a 2 foot carrot? I know it won't be very pleasant for either of us or necessary, but we will reach the ability to feel connected that way!
EDIT: Why don't we just put a concrete wall between us and cut a hole for the didlo to go trough? Then we will both know that somewhere out there there is another guy, but they cannot interact with us! Don't worry, you can rely me on bringing you the true SimCity experience!