Well presumably they do it to make money. And they definitely arent going to get rid of the screen. Used for backup camera and other stuff. Backup cameras are required by law in the US on new cars.
Due to safety and emissions regulations we just cant have a dead simple car even as a niche option.
They could charge for the screen and give the option to use a connected phone as screen instead. To use that phone you'd have to install the car manufacturer's app which could leech data from the user whether it was anywhere near the car or not.
Another alternative would be to use the dashboard screen - where the speedometer etc. used to be - to show the backup camera image, the speedometer isn't really needed when backing up anyway.
> Backup cameras are required by law in the US on new cars.
This didn't used to be true and I'm not sure if it is now but it is required in California, which is why they are ubiquitous. Fun fact.