Caterpillar does it with phones[1], and their main business is heavy industry. Why not auto manufacturers? Could easier access to smaller process nodes incentivize them to branch out into new markets like that?
When I looked into it, the most cited reasons were "that's not our business" (really? then what is?) and "it costs more than it's worth" (it doesn't, plus you get government subsidies for green initiatives).
No mention of contracts forbidding that, some manufacturers do forbid resale of whole units, but not of spare parts.
Caterpillar sold/licensed their brand for use in industries they're not competing in, btw, just like many other big companies.
Appliances aren’t quite as complicated, but I could still see how it would be a big change from the perspective of how they do business.