I think it harkens back to the days (pre '80s) when MB's were designed by engineers instead of stylists...okay an exaggeration but hear me out.
Older MB's were notoriously efficient in design...larger steering wheels for optimal leverage, hard seats for long distance support, power windows EXCEPT on the drivers door (cause you can reach it) and exterior mirrors designed to show you what you need to see. On the passenger side they are narrow and tall to cover the rear quarter blind spot, whereas on the drivers side they are wide to show the road behind.
North Americans, not used to form following function, called these quirks "the arrogance of Mercedes engineers" and eventually the stylists won more influence over design, it seems.
