In some countries it's a legal requirement to have a backup camera, which means you need a screen to display it, and hardware to render it.
> and hardware to render it
Not really, you legally could have a video camera and a CRT as a backup camera. I wouldn't say that anything is rendered in an analog video system.
I have always thought they should put the display for the backup camera behind the driver and facing the front of the car, so that it would be easily visible to a driver looking out the rear and rear-side windows while backing up.