Building below ground would probably more than double the cost. You have to dig, possibly blast (in the city) the dirt. You’d have to move the dirt somewhere else. You’d have to not only waterproof the structure, but you’d need special equipment running 24/7 to dehumidify the air. Probably the crew and worker types you’d need for the dig phase are not the same as the ones you’d use to build the structure and you’d have to find them somewhere as they probably don’t live and work nearby. I’m sure there are other issues I haven’t listed.
I agree, but filling in the hole afterwards saves everyone so much money.