> Another way to look at this has nothing to do with conformism. Whereas a suit says "I feel the need to dress to impress you", casual wear says "I don't need to dress to impress you, that's not why you're going to hire me".

Except that, in any community where the maxim you state is broadly known to be applied, the actual meaning is reversed, since anyone who is aware of the maxim and wishes to dress to impress will wear casual clothes, wherease anyone aware of the maxim who continues to wear business clothes will be doing flying in the face of the maxim in the same way that someone wearing casual clothes to an interview in a more traditional environment would be.