Earlier quoted context omitted.
People would grind off the serial numbers and sell them on the secondary market, or for the metals. With motorcycles, for example, motors and frames have vin numbers stamped to help prevent this, but you’ll sometimes see cheap parts for sale with the vin cleaned off.
In case anyone thinks this is cost prohibitive or the tooling is rare, a $100 battery powered grinder you can buy from Home Depot will do this in five seconds. If you have a little less money and a little more time, a $5 flat file will do the same thing in a few minutes.
So whomever grind the numbers off, may as well cut it open and extract the metals. It puts a major obstacle in the supply chain.