Why is it that kitties like boxes?

I have had this particular box for two weeks. Since I unpacked the Amazon order that came in it. Every time I go to put it in the recycling, there is a cat in residence. It remains the most popular cat hang out in our house.

Morty loves it.

Orange Kitty loves it. He was the first to try it as soon as the packing came out.

Have you heard the saying “as happy as a pig in mud”? I think that should be “as happy as a cat in a box”. That’s apparently where all the cool cats hang out.

I’m contemplating wallpapering it and adding a bed.