What connection does huckleberry Finn see between the duke and the king and real royalty?

In "The Adventures of Huckleberry Finn," it doesn't take long for Huck to see the Duke and the Dauphin as plain old con men. He states that all royalty, whether they are the real thing or just imposters, are a pretty bad lot, out to take what they can. He felt it was best to leave them to their own devices since they probably just weren't raised right.