All of my games have cardboard boxes. This was because A video rental store let me have their stock, and the cardboard boxes were shrink-wrapped and used for a person to bring to a counter in order to rent a game. The games were kept behind the counter.
I opened a lot of the empty boxes to find out what was jingling around in them. It was a store alarm sticker with the wax paper backing still on, it wasn't stuck to the cardboard inside. This alarm decal was so no one would walk out with a box and steal the box. Without a box, it's a bit more difficult to rent a game.
Also inside, were all the pack-in papers - Turbo gear catalog, usually.
After that, for any other used games I wanted, I just made sure to buy it with the box. However, by then, I had nearly all the game sin boxes since when I bought TG-16 games, I saved the boxes anyway.
I did throw out a box for my Turbo Booster. It was beat-up to begin with, being Toys 'R Us old clearance, red price tags and all. It just got more beat up as I had it. It was horrible looking, so I chucked it in the trash.
.