Depends on the size. My girlfriend runs a business out of the house (formalwear alterations by mail,) and her day job is in advertising/merchandising so we’re always inundated in cardboard boxes. If a box could be used to ship out completed dresses, we’d probably use it for that. If larger, straight to recycling. I’m still hoping my cat will go sit in them someday, so I leave them around.
Same thing I do with every cardboard box: initially leave it on the ground for the cat to play in inevitably he will get bored (we’re talking a timeframe of minutes here) and then continue to leave it on the ground with the promise that I’ll break it down later. allow it to collect other cardboard boxes, as apparently this is now the “box for boxes”.