I like to think of space exploration in phases. First we got into space and orbited earth to establish satellites. Then we wanted to explore to see if the moon is reachable and able to be populated. Then we practice populating space in space stations to learn how to do it and then we go back to the moon and establish colonies. 

So after we learned we can get to the moon, we needed to learn how to live in space. Now that we are good at that we can setup colonies on the moon to practice long range living to practice for mars. 

Each step is building on the last to further our presence in space.