Why do we die?
Maybe because a steady flow of new people is the only way for new social structures, paradigms, and ideas to evolve, which may in turn maximize the chance of the survival of life. As Nobel physicist Max Plank said about evolution in science:
"A new scientific truth does not triumph by convincing its
opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with the idea from the beginning."