Establishing colonies, for one.
Humans learning how to live and work in space is important for establishing colonies. There will come a day when it is time for humans to live on the Moon, Mars, and other worlds. We need to become a multi-world species. Why? I think it is important for our survival. It gives of room to expand our physical presence and our knowledge. We will take what we learn living and working in space and grow with that.
Don’t get me wrong. I am proud of our robot explorers. They have done wonders and have taught us a lot, but I think it is time for humans to get out there permanently and start learning how to live off the land.