There have been millions of examples of employees stealing items by claiming that they were junk, or had been on the clearance table too long. So that's why companies demand that such items are destroyed...to take away that excuse from thieving employees.
When I was a young service manager at Goodyear, we replaced tires under warranty, then tagged them and stored them until we got instructions on what to do with them from corporate offices. A few days later we would either ship them back to Goodyear, or be directed to cut the beads with bolt cutters, and throw them in our scrap tire pile. And if you did anything else with those tires after getting disposal instructions, it was automatic termination. But often tires had been replaced just to satisfy an irate customer, when there was nothing wrong with the tires at all. So now and then the warranty-replaced tires ended up on tech's personal cars. And, occasionally, someone would get caught, and fired immediately.