We are monkeys that with the benefit of lots of time have developed opposable thumbs, tools, and language. We used language to describe abstract concepts in words. One of those words is “legacy.” Some people are driven to build one. Some are just altruistic. The urge to create offspring is also common and with it the hope your brats will fare well. There are your reasons why some people build for a tomorrow that never pays them back.

Consider also that somebody has built the road that leads to your house, the city you’re in, the hospital you go to when you’re sick. Civilization is a chain of paying stuff forward for those who come after you.