Stop in for a cup of coffee

From time to time I look at house ads, most often with a basement, and almost always in areas where it is frost and snow in the winter. And it is one thing that puzzles me. In the ads with pictures from the basement, I almost never see insulation in the roof in the basement, which is the floor at the first level of the home. These puzzles me greatly, because our house here does not have a basement, but there is a crawl space under. I have never been there, but the floor is cold. So, now I wonder if it is no insulation here either, and I know for a fact that there is no insulation in the floor / roof between the first and second level.
Is this a common thing, not to have insulation in the floors in the US ? And if that is the case, for what reason ? I am used to 8 inches of insulation in the floors, 6 in the walls, and 14 in the roofs. Either a glass based insulation a bit like Owens corning, or Rockwool.

Bill
Can't speak to newer houses but older houses rarely had any insulation. If not - first place it was added was the attic floor, then walls.
With central heat and hot water - the furnace and heater was usually in the basement. The heat from the furnace warms the floor so really no reason to insulate.
Over the coal bin - that's where I'll sometimes see the cieling above covered.