What effects do authorial intrusion yield in The Crucible by Arthur Miller?

In The Crucible, the major effect of Arthur Miller's authorial intrusions is to give us deeper insights into the characters.  As a play, this text lacks a narrator who can explain what characters are thinking or feeling, and Miller's interjections function in much the same way that such a narrator would.  He explains the motivations of certain characters—Mr. Putnam is bitter about the fact that he gets shut down by the town almost every time he tries to do anything. Proctor feels like a fraud, although no sign of this has been betrayed to his neighbors yet, and we learn about their deep-seated feelings (which would likely remain hidden for much of the text if Miller didn't tell us about them).