No fun in keeping a group united if each one has interests elsewhere.
But there is no fun in being selfish and greedy either.
Most people wants only his/her own good.
Like you wrote that "I think we are divided more because of our egos than because of any of society's structures".
Many people think that humans is at the top, but the reality is the fact that humanity is deep down somewhere. Probably in the deepest depths somewhere.
Yeah, we might be actually at the lower tiers of the awareness chain. Finally we go back to balance, a bit of sharing, a bit of taking care of yourself. There's enough for everyone and everything when you open yourself to broader perception.