It is simply crazy. Unfortunately car design now seems to be dominated by an obsession with appearance rather than practicality.

On a personal level I have discounted buying a number of cars because of, in my opinion,

a dangerous lack of visibility.

Why do most manufacturers make a large rear windscreen on the vehicles and then spend money blacking out large areas on the inside, making the vehicle claustrophobic?

I agree with this sentiment, up to a point. But allow for (a) gluing the edges to the metal frame (b) the printed circuitry for the heater element and (c) aiming for continuous glass on the exterior, and the transparent area must be much less than the overall glass.

Being able to see out seems to take a steadily lower priority on the stylist's drawing board, possibly working towards the promised driverless cars we read about. Strange though that some models fit a 'panoramic glass roof' which can't be opened and only serves to increase the need for using the air-con.

Pushes up the sale of expensive (profitable) options such as parking sensors and reversing cameras

I know not everyone agrees but I am certainly one of those who thinks that rear visibility is important, even if you do have decent door mirrors.

One can never eliminate the risk of reversing into someone- particularly a child - but those who design cars should do all they can to minimise that risk.