The reason, of course, is the virtue that permeates George Bailey's life. He gives many a person a break, charity, if you will. He has a network of friends that are not on Facebook, that even he doesn't realize he has.
Hannah, the main character, has a dependable friend in Jason, but feels quite isolated, and there are good reasons for her feelings.
Hannah is a walking contradiction, like one who inspired her character, Gianna Jessen. To be an "abortion survivor" is to be caught up in a debate by the nature of one's very existence. She is, as it were, the opposite of George Bailey, she was supposed to not have a wonderful life, or even to be considered a human person at all, and simply vanish from the scene like a character leaving the stage (or some might say a prop).
But, George Bailey's vision of life without him is pure fantasy. Abortion survivors are a reality that makes some people uncomfortable. This movie puts that reality out to an audience in a new way--not with the story of Gianna Jessen, but with a fictional story that is designed to reframe debates about the nature of human life. A powerful moment for me was when Hannah writes in her journal, "The truth will make you free?" We've probably heard the phrase, "What is truth?" but here another famous statement is framed as a question, and the question is a big part of the movie. Inevitably, though, forgiveness is a bigger part. Although I don't think the phrase "divine mercy" occurs in the movie, it is an underlying theme. Truth and mercy meet.