Which is pretty much my whole point.
There is no GOOD reason to put everything in a car on the same network where one small failure can disable the entire vehicle.
None, zero, period.
Just like the oil-bath toothed "rubber" timing belts that are falling out of favor, it was embraced by the automotive industry, monkey-see, monkey-do, because it was new and different, and helped to ensure rapid unsupported system obsolescence and therefore lessened used-car usefulness, reliability, repairability, and value...not because it was more robust, cheaper, or lighter as is widely rebleated.
And although a lot is written about "robustness" and "fault tolerance" and "wiring simplification", anyone working boots-on-the-ground in the post-warranty service end of the automobile industry knows this to be largely bull.