Are they actually paying? As far as I know, the power in this relationship is the other way around, with the car manufacturer having to pay (to programmers) to build protocol support on their end. Note also what I wrote about AV cars (EDIT: that was an edit a minute or so after, so you may have not noticed).

Probably because software will be the most important criterion for choosing a car and you as a manufacturer won't be replaced by Google and Apple (who both develop their own cars). However, you suck at developing software and people are already using Google and Apple, so you will get replaced by Google and Apple anyway.