There's big savings in heating and cooling costs from using the earth for thermal balance. And thousands of wasted square feet below our feet.
Elon Musk is forward thinking with his Boring Company.
If civilization survives, besides outer space, the next frontier may be under the surface of the planet. Developing technology is now making this virtually untapped space accessible and usable.
A home in a mountain near the top would be a good place to view the chaos below.
VonBraun wroite a story about the notion, on Mars.