I have a few theories that feed this thought.
1. We are always comparing and competing against each other. We do this geographically and individually. As a country, our people must be better than another country. "The Smiths" vs. "The Jones" in the neighborhood. He just had a garage added. I must have a garage and another story. She has bigger boobs. I must compensate by driving a nicer car... and so on.
2. We always strive to better ourselves for survival of our species.
3. By nature, we are curious.