This may be a contributing factor, especially in places where they are building small apartment building and each has a garage, but I don't think it's a dominan

This may be a contributing factor, especially in places where they are building small apartment building and each has a garage, but I don't think it's a dominant factor. First, a couple of ramps that go underground is really not that much space in the footing of a big tower. I see old neighborhoods with lots of shops that nevertheless have underground garages. Second, I don't think shops are that deep. New city blocks, especially hosting skyscrapers, are much deeper than the typical blocks in (say) the West Village. Those shops seem to do fine with very little floorspace.