I feel like automatic headlights should be mandatory. In my state, if your wipers are on, your lights should be on. Even during the day rain can make it difficult to see cars that don't have their headlights on and therefore don't have red lights on in the rear. I see many people driving around at night with no lights on and it's a safety hazard. Additionally, your dash lights will be at full brightness when the headlights are off so now your eyes can see even less light coming through the windshield. If relatively expensive backup camera and a display to show it can be mandated, then a much cheaper photodiode to switch on some lights should definitely mandatory.
I wonder if the insurance lobby was the one that pushed for backup cameras, it's probably greatly reduced the number of rear collisions that they have to pay out.