I think it's because existentially, it doesn't really matter if you live 80 years or until the final heat-death of the universe. When you get to the end, you'll

I think it's because existentially, it doesn't really matter if you live 80 years or until the final heat-death of the universe. When you get to the end, you'll still want to live longer and marvel at how fast it all went by. The miracle is that we existed at all, and that we recognized ourselves (or whatever consciousness is). Next to that, duration is insignificant. A scale mismatch.