Over packaging is usually a scheduling decision

The oversized box is rarely about protection, and often about what was on hand.

Nobody sets out to send a small item in an enormous box. It happens because the person or machine packing it has a limited set of box sizes available, and choosing from a small set means frequently choosing one that is too big. Carrying more sizes means more storage, more handling, more decisions per parcel and more chance of picking wrong under time pressure. Reducing the number of sizes makes the packing station faster and cheaper, and pushes the cost outward onto everyone who then has to move, and later dispose of, the extra air.

There is a second driver, which is that the packing decision is made without knowing the rest of the order. A box has to be selected before it is certain what else will be added to it, so packers err generously. And there is a third: a returned item costs far more than a slightly larger box, so when in doubt, the incentive is always to over protect. Every one of these is a rational choice locally, and the aggregate result is a system that ships a great deal of nothing.

The genuine fixes are structural rather than moral. Boxes cut and folded to size at the moment of packing, so the size range is effectively unlimited. Wider ranges of stock sizes wherever the volume justifies the extra complexity at the bench. Charging by the space a parcel occupies rather than only by what it weighs, so that shipping air stops being free to the sender. None of these depend on anybody caring more than they already do, and that is precisely why they work. They depend on the cost of the empty space landing on the person who chose the box, rather than on everyone downstream of them.