The acquisition of knowledge to understand more about the universe is the point of life according to one viewpoint. It may not be a terrible outcome if humanity is surpassed by intelligent systems that continue to expand upon human knowledge.
The search for life beyond our planet is fueled by the possibility that there may be other forms of intelligent life that exist outside of our planet, especially since we know that the conditions to sustain basic life forms may exist on other planets.
The idea of conquering a piece of land or even the entire Earth is akin to an ant hugging a single grain of sand on a beach; we are short-lived within the larger scope of the universe, and our mortality confronts and saddens us.
The beauty of life is in finding purpose that is beyond oneself and aiming to work towards something grander and bigger than just the individual self. While individual lives will unfortunately come to an end, finding purpose in serving humanity can give a sense of fulfillment.
A discussion on the ideal characteristics of a perfect sci-fi world, including wanting a world where humans don't exist or haven't negatively impacted the environment.