But until recently, we at least owned our incidentals – the small-potatoes stuff, like the clothes on our backs. Our cars.
Our tractors, certainly.
Not if it's a John Deere tractor.
When you buy one, you're actually purchasing an "implied license for the life of the vehicle to operate the vehicle." Basically, a rental contract. With the difference being that even when the rental is paid off, you are still bound by the contract.
It has to do with two things – the code that runs the tractor (yes, them too) and the ownership claims to that code asserted under the Digital Millennium Copyright Act (DMCA).