How do the duke and king entice people to see the "Royal Nonesuch"? What do you think Twain is implying about human nature with this?

They put on the playbill that women and children are not allowed to attend.  It plays on people's want of the forbidden fruit.  People want what they can't have.  The scandalizing part of it being only for men makes men want to come.  It also shows the sexism of the time by believing it is only appropriate for men.