In one century you will be dead and so will everyone that you know today. In one thousand years nothing about you will be remembered, and nothing that you did while you were alive will matter at all. In one million years this world may not even still have the human species on it. One day in the distant future, but a day that is going to one day be here nonetheless the world will end. All life on it will be destroyed and it will be nothing more than a rock floating in space… one day there will not even be that rock. It is possible that our species, or potentially another one from Earth will be able to start colonizing other planets in other solar systems before our planet dies or our sun explodes.
All other species that we have known live for food. They live, eat, multiply and die. That is the most that any other species seeks to accomplish in existence.
We want more, we want a purpose, a meaning to our lives, something that we are all living to accomplish. Individually our lives are too short, and as a species we will most likely all one day completely perish. If we do colonize, then I suppose there is a possibility of our species continuing on for millennia, but does that actually mean it will ever amount to anything more than merely existing.
No other creature that we are aware of asks for anything more than to exist for as long as they can maintain themselves. We do not stop there. We want to have a reason for being. We want the universe to need us for something, to amount to more than what we are. However, us wanting it to be that way will not make it so.
I do not know what the future holds, but in a situation where existence is all but guaranteed to end one day why ask for anything more than the precious little time you actually get. Even if the unlikely happens and our existence serves an actual purpose, no one alive today will ever realize that purpose. Life is pointless but it is still life, and that is better than the alternative.