The Dark Tower is a story which employs and studies the concept of personal honor. As I see it, the protagonists begin their perosnal and collective quests as a matter of honor, a quality which moves people forward to do good works and which, if honored, prevents them from doing bad. This quality of honor, this reason they exist, must never be forgotten by characters in The Dark Tower world, so is reinforced by reminders summed up in ideas such as "for the sake of your Father" and "you've forgotten the face of your Father". A father might be the first, singular personal figure one thinks of in terms of the idea of honor. I think in literature it has historically been so.