This is going to sound like I am depressed, and I am not. But a lot of what people do is really just filling in our time until we die. Watching TV, MNing, going for walks. All just ways ultimately of using up the hours we have.
I guess this is more an existential question. If you are religious there is an obvious purpose to life. On a biological level the purpose of life is simply survival of the species - individuals don't matter. On an individual non religious level, life doesn't really seem to have any purpose. We are simply filling in our time till death, and on the way if we are decent people, trying to help others avoid too much pain.