Because Amazon itself is usually handling the storage and shipping -- you can't pay Amazon to store empty boxes in its warehouses. (With perhaps one exception:

Because Amazon itself is usually handling the storage and shipping -- you can't pay Amazon to store empty boxes in its warehouses. (With perhaps one exception: https://www.amazon.com/Cheap-Moving-Boxes-10-Pack-10MPK/dp/B00U62GPLK/ref=sr_1_1_sspa?dchild=1&keywords=cardboard+box&qid=1613453694&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzQ0szMjFXWlowRzEyJmVuY3J5cHRlZElkPUEwODkwMzMzUEs0ODJYMzNUNkVSJmVuY3J5cHRlZEFkSWQ9QTA4NDMwNzUyQkxVQUE4U1ZaVFNGJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ== https://www.amazon.com/Cheap-Moving-Boxes-10-Pack-10MPK/dp/B... )