Assuming you’re referring to The Crucible, their scenes are significant because usually they show that Proctor, despite his attempts to be a good man, struggles deeply with himself and his faith. Elizabeth, on the other hand, is a much better individual and is forced to live with the fact that her husband had an affair with Abigail. However, she insists that he is a good man throughout their interactions, even when Proctor himself doesn’t believe it. It shows that even though he betrayed her, she still sees the good in him