I mainly see space exploration as an end itself as opposed to being "for" anything. It's not so much a place to live and colonize, but something to further explore. No matter how bad the Earth gets, it's going to be nicer than any of the other solar bodies, which are already pretty terrible for human habitation in pretty much every way.

Main advantage of a moonbase or orbital base would be cost and accessibility. It's a lot easier to launch from the moon, if we did some of our construction and industry there. A lot of which could be automated eventually, you wouldn't need a whole population there. More an outpost than a colony.

I'm sure colonies would appear eventually, but not in our lifetimes. But simply trying to put anything substantial up there would drive further advancements in the field.