they want to lock you in to oem parts because otherwise people might use their tractor for 30 years before buying a new one

same reason car dealerships want you to only go to them for maintenance

Not just eom parts, also OEM service.

Which is a huge problem when you live in bum fuck nowhere like many farmers.

right but without the part supply under control someone could just do it themselves so they need both, though it's true plenty damage is done software-only