Other than the adventure of it, for those who may want that kind of adventure, I don't see the usefulness of colonizing off-Earth climes. If the thought is that we will need to escape the planet because humans ruined it, well...

I've always been more attracted to putting my efforts into fixer-uppers and restorations than in breaking new ground.

You never change things by fighting the existing reality.
To change something, build a new model that makes the old model obsolete.
R. Buckminster Fuller