Lol, 1 to 4 is just called "knowing how to drive". These cameras aren't a serious value add unless you're driving a massive tank, err car.
There are hundreds of millions of drivers with new ones entering and old ones exiting the roads all the time.
If you want to practically improve safety you have to make the vehicles safer, you can't just hope pointing fingers at bad drivers is gonna do anything.
So many parents ran over their own child that backup cameras are now mandatory in the US.
So yes everyone is right, yes a lots of people are just bad at taking basic safety measures but backup cameras are still a necessity because this will not change, it is even worse with people doomscrolling their smartphone while driving.
How does that help other people walking down a sidewalk?
Yes, in principle one could take whatever other measures necessary to prevent such accidents. In reality, backup cameras save lives. Just like seatbelts, anti-lock brakes, crash safety standards, and other safety features that "Real Manly Drivers" protested against back in the day.