Imagine a world with no currency, where everyone does work for the better of their community as a whole. This causes no war, no jealousy, and no conflict. This world, however, cannot exist, because our human race is intrinsically selfish. We have to have more than the person next to us. If we don't, we cannot be happy in that situation.
I'm not trying to say you need to have everything to be happy, but there is a part of all of us that wants to have more than our neighbors.