Well you see, we need windows so we can see all the grey and tan boxes outside. How could we live without the starless night sky? Or the ten minutes of sun through your window by the time you get home from work?

But in all seriousness, You need jobs first and foremost because otherwise everyone would just rather live rurally. You wouldn’t want it to become a company town nor ghost city, so there would have to be a heavy investment by dense congregation of successful businesses. You’d basically have to decide how deep you’re going to go, then tunnel massive amounts of sewer type systems beneath that. The biggest thing imo is dealing with heavy gasses. That is a lot of expensive infrastructure to prepare very deep, before anyone can even start thinking about living spaces. Beyond that, I don’t think the challenges outweigh the challenges we face now and in the near future. We’ve adapted to those, we could adapt to more, but it’d be a lot of expensive learning experiences in the mean time.

It might help to frame it as living under a park, or living within walking distance of businesses that necessitate or benefit directly from being outside. Like cheap food from small farms maybe. Termites massively out-number humans by mass, but they seem to make a pretty good go of it without devastating their ecologies.