Instead of the box that the bed came in being used as the bed by your cat, this time the box contains a box and that becomes the bed! It sort of makes sense. We know how cats don’t necessarily respond to commercially made products as we do because the products are made for us ultimately because we are the purchasers. Cats respond to things that push their go button and their button is usually different to ours. It could be almost anything but they do like boxes, we know that. I have a theory about why cats like boxes.
I’m a bit surprised, actually, that nobody else came up with this idea before or perhaps they did?