Old school manufacturer mentality, although it's not completely baseless...
- Don't give up control of a safety critical interface
- Don't give up data (which they think they can monetize) by not controlling the full stack
- Don't give up a branded differentiator like "iDrive" for what everyone else is offering
- Don't pay a tax on our cars to big tech if we can avoid it (see how they dragged their feet on Carplay to start)