They stayed open in the past, not for the business, but more for the need to do various operations when there are no or few customers around: cleaning, accounting, prep work, inventory, stocking, repairs, etc… Over the last twenty years, everything has gotten more efficient, and these operations can be forced into "late" night (after 8pm) or early morning (about 5 to 7 am). No need to keep the place open all night any longer. This was all happening slowly prior to COVID.