For most (not all!) of that complexity, if it fails you're left with an inoperable part of the car, not an inoperable car.
I've got a 2011 Hyundai that's...well, it's got all sorts of problems, most likely caused by the chipmunks that call it home . The backup camera doesn't work and stereo system is silent.
But the car still drives just fine, those systems don't cause a full failure of the vehicle. The screen goes black when backing up of course, but I can still back up.
This is all find and dandy until your local predatory BHPH car lots and safety sallies join forces and lobby to have your backup camera make it onto the list of stuff that gets checked as part of annual safety inspection in your state.
It is highly unlikely that equipment not originally mandated fleet-wide will be force-checked upon anyone. I have a car without backup lights in a fairly strict state and it passes just fine as it was not originally equipped with backup lights. (I could, at least in theory, pass without seatbelts as well, but that would be idiotic.)
My State shows up as Yellow... There is only 1 city that most of us in the state believe actually should be a part of the neighboring blue state that requires testing for 99% of people in my state no testing is required, I have a feeling many of the red states on that map are the same.
Note that a lot of those states with "emissions inspections required" amount to "if the car is OBD2 [Model Year 1996+], it must be READY and have no emissions-related faults set; all non-OBD2 cars are exempted, absent visible exhaust smoke".
I've got a 2011 Hyundai that's...well, it's got all sorts of problems, most likely caused by the chipmunks that call it home . The backup camera doesn't work and stereo system is silent.
But the car still drives just fine, those systems don't cause a full failure of the vehicle. The screen goes black when backing up of course, but I can still back up.