Why is Creon not the main character in Antigone?

One of the lasting debates about Sophocles’ Antigone focuses on whether the main tragic figure in the play is Antigone or Creon. Antigone is a more sympathetic character than Creon, and she also exhibits some of the characteristics of a tragic figure—through her own pride and actions, she suffers a reversal of fortune. Further, she is the daughter of Oedipus, and the other two of Sophocles’ Theban plays focus on Oedipus and his family. This may indicate that she is the main focus of this play as it follows the theme of the tragedy of the family of Oedipus. It is also worth noting that the title Antigone was ascribed to the play be readers who found Antigone to be the main focus of the play (we do not know what title, if any, was given to the play by Sophocles).
What creates uncertainty regarding who should be considered the main tragic figure in the play is that Creon also exhibits the characteristics of a tragic figure, and some even read Creon as being the more prominent tragic figure. His fall, within the context of the play itself, is greater and more complete than Antigone’s fall, in the sense that he has to live with the deaths of his loved ones, which his actions wrought. Further, Creon comes to recognize his own fall, and the reasons for it, in a way that Antigone, who goes to death defiant and proud, does not. In this way, Creon seems to be a more likely candidate for the main tragic figure. 
However, perhaps a more complete understanding of the play is that both Antigone and Creon are tragic figures, and that neither character's role in the play is more prominent than the other character's role, at least in terms of who the main tragic figure is. So while modern readers will likely see Antigone as the main character, as she is more sympathetic and seems to fit the mold of a protagonist, and the less sympathetic Creon as the antagonist, it seems quite possible that Sophocles intended a more complex understanding of the roles of the two main characters in the play Antigone.