Your car is running a hell of a lot more software than what you've just described. The ECU manages the engine; the BCM manages lights, wipers, airbags, and seat

Your car is running a hell of a lot more software than what you've just described. The ECU manages the engine; the BCM manages lights, wipers, airbags, and seatbelt pre-tensioners; you'll also have ABS (anti-lock brakes, so you can steer while braking instead of plowing straight ahead regardless of the orientation of your wheels) and either Traction Control or Electronic Stability Control. Every single one of these things is safety-critical, whose failure could cause a crash before you can react to it. It's this software that's written to the MISRA standards.