It is simple really MB's are expensive cars and people think you have money. I would imagin the Rolls/Bently crowed gets it worse. Personally I like the attention a clean MB can get you, sometimes it can open doors.
I get the same thing when I am working on boats for people I know. No one will give you the time of day when your washing a small center console. But when I'm having lunch on the back of a $1m sportfish well then all of a sudden people want to be your friend.
It is annoying.