Exactly, an important endeavor for mankind is to gain new knowledge whether or not it has immediate applicability. Only when new knowledge is discovered can we then find new applications for it. Lets say in thousands of years, some global catastrophe happens and Earth is no longer habitable. All the advances in propulsion and planetary exploration could allow our species to flee to a new planet and make it just like earth was. Our descendants would be very thankful that society decided to pursue this knowledge long before.