Originally Posted by Rudyk
I'll buy that the back seat prongs are for bag attachments... don't look too study in my view.
Their height is such that they don't need to bear significant weight. If we're talking of a standard plastic grocery bag, the weight of the objects (like a gallon of milk) will rest on the floor. The hook is at the perfect height to hang the handles on; they are placed so that there isn't enough slack for the handles to fall off, but not so high that it would need to bear weight beyond that of just holding things upright.