I am really in a quandary about this paint issue.
I honestly agree .... there is no need to paint unseen area .... including beneath the floor carpet and other upholstered areas.
But I draw the line on the door jambs. Leaving the door jambs primed, but unpainted is not acceptable.
The door jamb is 1) visible, 2) immediately adjacent to a painted finish, and 3} embarrassing when showing off your new $50k vehicle to family and friends. Supporters will say it saves weight, costs ........... I say it is unbecoming to see primer on such an expensive car.
I really don't care how Mercedes, or any other manufacturer handles the situation.
I don't want to see unpainted primer in such a conspicuous location every time I enter and exit the vehicle.