According to some people, our only purpose in life is to reproduce before we die.
Presently I do not desire to reproduce as I find the idea unappealing to me. But I really don't care much if my genes aren't passed on - besides, offspring can easily be killed off somewhere down the line, ending that person's legacy. (Not that the great great grandparents will care if they're dead by that time) I suppose I can't rule out that the desire may change one day if that gene that dictates my desire to procreate turns on. I don't know why it hasn't turned on already really, considering that I'm of the ideal breeding age of 20.
But why does nature consider it a necessity? All life forms live to reproduce and pass on their own genetic material again and again and again until they evolve into something else or eventually go extinct? It just seems so pointless.
Even the earth we live on is only temporary so unless we find a way to colonize another planet or somehow evolve again to adapt to living in space or something what's the point of survival? We're always struggling to survive and yet we find some pleasures in life that encourage us to keep going.