If I sell you copyright of my code, I might still have it on my computer but I lost any rights to use it. This is a standard business arrangement that anyone on this site knows and uses. I don't think it's as complicated as you make it sound.
Just step back and think about how irrational this is. Abstract constructs like this are arbitrary.
Yes, it's arbitrary - just like practically everything else. Having to drive my car on a road and not kill anyone is arbitrary, but leads to good outcomes.