People may want to be free individuals, but they also want to shape the world around them, and feel part of that world. The urges to help and to belong are as strong as, if not stronger than the urges to gain, and be independent.

When people participate and share resources, they're not just being selfless, they're influencing their environment to how they want it to be, because participation is the easiest way to do that, not power. We all gain something from giving.