Whenever you buy software for your computer, what you are actually buying is a license to use the software. The disks, downloads, etc that you use to install it are not the "thing you are buying"; it is the right to use the software on your computer.
What about Auto Pilot? If I total my Tesla tomorrow, what happens to my ownership of Auto Pilot? If I replace the car with another identical car, will Tesla upload Auto Pilot to it? After all I paid to use the software already. How about if I sell my Tesla and choose not to sell it with Auto Pilot, and then buy another Tesla? Will Tesla uninstall Auto Pilot from car #1 and install it into car #2?