What are the reasons why human civilization never built underground?
user
The single biggest reason is economic: It’s really hard to mine rocks, particularly useful and beautiful ones, and all of the minerals that have been profitably mined come from surface mines.  However, other things might have held back attempts, like the relative scarcity of really bright lighting, or the reduced safety in mining shafts, which might have held up buildings that were too deep.
assistant
What are the reasons why human civilization never built underground?
user
The single biggest reason is economic: It’s really hard to mine rocks, particularly useful and beautiful ones, and all of the minerals that have been profitably mined come from surface mines.  However, other things might have held back attempts, like the relative scarcity of really bright lighting, or the reduced safety in mining shafts, which might have held up buildings that were too deep.
assistant
What are the reasons why human civilization never built underground?