Human constructs (marriage, legal justice) align what seems to be the world with our ideal senses of morality. In the real world cruelty is rewarded and most suffer. Suffering is a constant which permeates into the nature of our fears, and as long as we can stave off our mortality we can feel "alive" and immortal, though that's still our survival insticts prompting us to make the best for the new generation. Noone wants to believe they truly will die, because they grew up in a culture that has conquered nearly every precursor to death, leaving those remaining alive as walking corpses whose ghastly presented remind us of our continuous decay. Old people slowly slough away their layers of vitality, suffering the half-deaths in their waning years of their eyesight, physicality, memory. It's nature reminding them that were not meant to stick around too long.
