Years back, I watched the video embedded in this article, and was instantly enthralled.
Once you hit “order”, from that moment, there is a pizza box in the world that’s ending up in the bin (hopefully the recycling). Now, if you’re eating a whole pizza, out of the box, that’s that. But if you’re sharing and/or can’t eat over the box, you’re likely to need plates. And if there’s leftovers, they’ll need something to go in, in the fridge. By putting perforations in the box, you allow the delivery box to fulfil these roles too. No plates, no tubs, no extra washing up. And that box still ends up in the same bin at the end of it all.
As the article points out, you can achieve similar results by taking to your pizza boxes with a sharp implement. But be safe with knives, y’all.