I bought a Hoover battery vacuum on Amazon a couple months ago. It was sold as new, but a bunch of separate parts all re-wrapped in poly bags arrived in a brown cardboard box. The wear marks showed that the battery had clearly been inserted into the charger a number of times. I actually phoned Amazon customer service and they apologized profusely for that screw-up. They sent me a new one in the manufacturer’s box and it arrived the next day. They said to keep the used one, too, and not return it — I was only charged once. That worked out well as we put the used one upstairs and kept the new one downstairs!
Lots of things are superseded by new models and the manufacturer would only destroy old inventory returned to them anyway. So they tell Amazon to keep it. As new models are introduced, sales of the old models declines quickly. So Amazon just destroys it. Either the manufacturer does or Amazon does.
When I worked for a company that manufactured cable TV equipment, we did the same thing. Our distributors in other countries would provide certificates from companies that destroy products attesting that the obsolete stuff was indeed destroyed.
We live in a really screwed up world.