Everyone who can afford a car with an infotainment system also has a high-end smart phone that they replace several times over the life of the car. It's not quite as bad an idea as putting a tablet in your refrigerator door, but the product lifespan mismatch is of the same nature.
To handle the case where the customer would prefer not to think about interfacing their phone or tablet to their car, a branded compatible tablet should be a dealer option, or at least the tablet-like part of infotainment should be replaceable.
In the US, reversing cameras have been mandatory since 2018, and in the EU since 2024, so any new car sold there will need a display for the camera output.
I wonder if the law specified a minimum display size and resolution, otherwise a car company could sell a car with an Apple-watch-sized display to save costs. I imagine selling a car where the display depends on the user's phone and complying with these laws will be virtually impossible.
I've seen cars that didn't have large screens put the reversing camera in the rear-view mirror - which actually is an excellent place for them.
The workaround I've seen was manufacturers putting reverse cameras in rear view mirrors.
I can't find a picture right now (man, internet search sucks nowadays), but e.g. lower trims of Kia Optima had it.