For the most part, the people who strip copper wiring for a quick buck would not know or care that selling it intact would make a lot more. They want cash now, not next week.
My guess would have been strain relief if something tripped over the wire and pulled on it. Instead of putting pressure on the port on the car, it will instead put pressure on the knot by the tire.
But looking at the other answers I guess I was wrong lol.