Qualification of a design takes a lot of time and money, and would need to be at least partially redone to replace a microcontroller. You need to be risk-averse

Qualification of a design takes a lot of time and money, and would need to be at least partially redone to replace a microcontroller. You need to be risk-averse when you sell hundreds of thousands of an expensive product with warrantees, and much more so when human safety is involved. I work in aerospace, not automotive, but I guess the industries are similar in that changing a microcontroller can easily take 1 year of time and 2-20 person-years of effort.