You are a French camping owner and you want your guests to keep their sanitary building tidy. You cannot easily turn this into a comprehensive icon. Of course it is tempting to put out a plain text sign reading "keep this area clean". But you know that your guests - however sympathetic they are -are human enough to display ignorant behavior in response to straight orders such as these. We all know what happens to commandments... This camping owner - or a smart employee - showed enough insight by putting the message into a kind request with a direct referral to one's own personal interest. Because in the end that is what we are sensitive and committed to. 
I don't believe that communications such as the above sign can turn true assholes into caring social human beings all of a sudden. But I do believe that this is a smart approach if you aim to activate at least the part of society that has a trace of common sense left in their heads. I think of this as a piece of real life 'strategic communications'.
