Because he's your father. Parents learn early on that being a parent means dealing with problems that aren't about them and being treated pretty badly at times, so they either run away from the responsibility or they stay and parent.
If he's still around to tell this to, then he'd have had to (at the very least) accept or (at the very most) embrace that that there was a chance his child would treat him badly and he had to go right on loving him or her.
[ooc: I'm not, just lodging my distress with the Society for Winchester Emo. ;)]