(here's your thread drift in the first responce to the OP, bam! Cause that's how I roll)
I always think that the diffrent disapline that most fathers use leads to a sort of right of passage for kids on to adulthood.
The moment where you buck up to dad, you are right to do so, and, as odd as it sounds, I think it's very important. With a good father, it isn't the end of being a dad or a sign of everything going to hell, it's that mark of "OK, you've made this decision based on adult rational thought and, while I might disagree with you, you're an all grown up now."
You don't have that moment with mothers as much, but the moment that you come to a point where you're both willing to defy the patirarch and can do so in a responcible and adult fasion is important.
I imagine, for the dads, it's also rather bittersweet. I know my Dad kind of shook he's head and had a sad smile.