While I agree entirely with your statement about automatics, I don't know why you single out Mercedes and Audi; there are plenty of both makes available with manual transmissions.Exactly!
when you have an auto gearbox car decides when to shift up or down and even in sport or manual simulation mode cannot keep the selected gear in the red rev's area.
Imagine being in the apex of a corner lift up a bit your foot from the throttle to place the car, and gearbox upshifts without your will to do so.
IMO i prefer total control of such a car. Even my Porsche Cayman S is manual.
On the other side, i couldn't even imagine a Merc or AUDI with manual, even they had 1000BHPs under the hood.