Well, as Mark Twain put it, "Clothes make the man. Naked people have little or no influence on society." Even societies which didn't have clothes as we consider them today have ornamental items worn as status symbols: Strings of beads, bones, ornamental paint, etc.
I'd say that wearing(or not wearing) appropriate clothes can impose a penalty or bonus on one's social skill checks. The exact effect of this is highly situational and is subject mostly to a DM call. Of course, if you're the emperor, nobody's going to tell you you're naked.