It is apparently an expected courtesy afforded British royalty during those times that their subjects refrain from addressing them directly.
In Chapter 10, not only does John Canty speak to Edward directly, he does so quite rudely, demanding that the boy "stand forth...(and) name thy name". Edward has already declared that he is a prince, but John Canty, who believes that the boy, who is dressed in rags, is his own son, berates him for what he sees is insolence, and threatens that should he "say (his) foolery again...(he should'st) not forget" what will happen to him. Edward is insulted to be spoken to in this way, and he "lift(s) a steady and indignant gaze to the man's face, and (says), ''Tis but ill-breeding in such as thou to command me to speak" (Chapter 10).
Edward, as a prince, is used to much better treatment than this, to say the least. The author, in satirizing British royalty during the time of Henry VIII, pokes fun at the excesses of the Court. The ritualistic courtesies afforded the royals borders on the ludicrous; Edward is accustomed to being waited on hand and foot. When he wishes to wash, a basin of water is brought to him, and a towel awaits when he is done. As he indignantly reminds Miles Hendon a little later in the narrative, subjects are not even allowed to "sit in the presence of the king" (Chapter 12).
That a common peasant such as John Canty should take the initiative to speak to a member of the royalty without being first addressed, and to speak with utmost rudeness at that, is unthinkable. Young Edward is aghast at Canty's insolent and base action, and attributes the man's behavior to his "ill-breeding" (Chapter 10).