You don't understand. Most car manufacturers have agreements with dealerships that will prevent OTA updates from being possible.
> Musk famously declared a while back that these are free for all other car companies to use in good faith
Yep, but 'good faith' means opening up their IP in return, more or less, so not many companies are taking that up. Anyhow Tesla still own the IP, so your original statement is incorrect.
There are also legal frameworks that make OTA updates edgy. Tesla is being investigated in germany because pushing additional features ("auto"pilot) might substantially alter the car from the approved version, leaving it without approval to drive on german roads.
OTA also suffers from all the beautiful issues that networked updates suffer from, most notably security, authentication, encryption. I for one prefer updates done via good old fashioned removable media.
So yes, OTA updates are nice, but I'm not certain I really really want that in my car.