In short, because sitting on a bar-stool type contraption (even if it has a back and a ledge for feet) is a very different feeling than sitting in a chair close

In short, because sitting on a bar-stool type contraption (even if it has a back and a ledge for feet) is a very different feeling than sitting in a chair closer to the floor, with feet on the ground. Also, invariably higher chairs tend to be narrower.