Because the moon is better when it's only a sliver and smiling. Duh. Besides, full circle mustaches would look dumb. [Whereas crescent moon mustaches are the height of fashion, evidently.]

[Have a continued blank stare Luffy. Marco is REALLY mysteriously old as hell. As it is, the Malnosso just gave him a time-smoosh since he's probably older than 40-something.] Rogers is just Rogers. Not as cool as Papa. He's not a King at anything. And pirates don't have royalty, yoi. That'd be weird!