Because profits. There is a business model and a lot of profit to be made forcing people to constantly a) pay for new equipment/devices, b) pay for any repairs or upgrades, and c) locking everyone into a single ecosystem.
I think it's something like that. I could be wrong.
If you BUY a tractor, you should be legally allowed to repair it yourself.
He clearly didn't have the funds and was at risk of losing the car with all the added mods.
Nobody should consider they own a car if it's financed. But they are liable for the bad things that can happen.