I think it is safe to say that most readers of this blog are primates. We are social animals, and humans are the most social primate of all. Orangutans are solitary, and 7 billion chimpanzees would never survive the crowding.
We know how to get along, the give and take of society. A big part of that is gratitude. Gratitude is more than keeping score of favors with other individuals, but it probably grows from that need. We’ve been able to abstract score-keeping into something bigger.
Gratitude works. We all need each other, and the more of us there are, the more that is true. Think about it.