Really? SpaceX made it over 90℅ cheaper to launch a rocket into space. That changes economic forces significantly already. Ancient humans walked continents and spread to the whole earth for no clear individual advantage (although perhaps a species advantage). Wanderlust and exploration appears ingrained in our species. It doesn't have to make (short term) sense for us to colonize other planets and stars, we are going to do it anyway. Politics change, technology grows at faster rates and culture will eventually support it. Why not?

We still have to fix our own planet's problems, but we can still colonize others. Some people will work on one and others will work on the other.