let me explain. attaching a non-essential sub-system with a large attack surface to a mission-critical network is not malicious (I hope) it is incompetence. I would accept a unidirectional serial link with a validated protocol as a sole connection between the two.

I think it is the same kind of thinking that goes into other bad ideas: flickering stop lights, red turn signals. The auto makers just don't really care or think. This is something I don't understand.