People who are around their fathers more than their mothers often have better character development and a lot more personal growth.
Most of the times, father's teach you discipline and humility a lot better than the mothers.
You have a point. There are differences between me and my half sister that you wouldn't believe (my dad married her mom and they lived in the same state/city) .
Not having a steady father figure in your life can either make or break you. I don't regret the way my parents did it though. They did what was best for them at the time. Not having a father and/or mother figure can make you insecure growing up and then you have holes that you have to fill, for a while that can be with sex or drugs or other vices. Until you realize there are more productive things like reading, writing, philosophy, "religion", spirituality, traveling..doing whatever necessary to better yourself spiritually, emotionally, mentally, physically.
And at first it does make you a little arrogant because since your birth society has presented you with stats saying you'll never be shyt and since you know how hard you had to work to get the essentials that others were born with then it can slightly affect your capacity to be humble about what you've accomplished.
And I understand its better to improve yourself from a place of security instead of a place of "let me show the world/myself what I can do"..but even if those same unstable/insecure people chose to get married, it might make society look favorably on the relationship but it doesn't mean that the situation is any better. Now instead of two "fukk ups" living apart, you have two "fukk ups" living together with a piece of paper validating their union. They're still fukk ups though.