There is something to be said for not putting all your eggs in one basket. If a big meteor headed for the Earth, we really could do nothing to stop it. It could be a mass extinction event, unless we have some humans someplace other than Earth. As for your depiction of lunar colony life, I think you are thinking way too small.
Not caves but rather man-made domes a mile across, filled with all sorts of vegetation. Plenty of air, water, and food, with no pollution of any kind. Even the light would be as bright as sunlight during the day, but with no sunburning UV. Best of all, you could strap on a pair of wings and fly. They could even have individual LED pixels on the ceilings so they could show the view outside during the night period, like the Las Vegas downtown aerial light show. They could project 5000 K bluish sky during the day. It would be hard to tell you were in a dome. And of course, there would be many of those domes, so you could visit other domes or go to live there. They could even have different climates. One a beach and lake dome, one a winter dome filled with snow so people could ski, many temperate domes, many 4 season domes, many tropical domes.
