Why does humanity as an "intelligent" species still fear death knowing it's the only thing guaranteed in life?

We've been around for a long time, we know that all life ends, yet almost everyone fears death. Why do we as a society still take death in a negative light even though we know everyone's gonna die? It's not just about one's own death either, people mourn and grieve when someone close to them dies, people also feel an unsettling feeling when they hear about an unknown person's death.

Is this purely biological? Will we as a society ever be able to get past the fear of death?