> I find it hard to believe it's cheaper to have all the cameras, chips, and other digital affordances rather than a small number of analog buttons and functions.

You should check how SW and HW are tested in the car.

A typical SW test is: Requirement: SW must drive a motor if voltage reaches 5 V. A typical SW test is: Increase the voltage to 5 V, see that the motor moves.

Now what happenes at 20 V is left as an exercise for the user.