I think that's where we differ in our basic philosophies. I personally would not choose to commit myself to that degree to another person, to spend that much of my life living intimately with them, and most especially not have children, unless we had first made the commitment that made it "official" to family, friends, God and ourselves. I just need that level of security for me and any potential children (because let's face it: having sex can yield children.)
But I am a risk adverse person and for me the risk is just way too high to do it any other way. I would never want to be that vulnerable or to have my children be that vulnerable. But often - as in your case - it turns out very well regardless and that awesome! There is just a awful lot of heartbreak in this world and it makes me sad and I'd love to see more of it circumvented. Granted, for plenty, there is heartbreak that happens after marriage, too.
Yes! That's it! There would no way on God's green earth that I would bring a child into the world with a man who was less than 100% committed to me. If we somehow happened to conceive that child before marriage, then we'd move up the date because I would want the security for my child. And, I'd have been ready and willing to marry him anyway. I too, am risk averse. In all honesty, there is no way I'd have sex with a man wihtout asking myself two questions that doubtless, some of you will laugh at.
(1.) What kind of child would I have with him? I don't mean this in the "perfect Aryan child" sense. But does his family have certain physical, psychological, emotional, legal issues that permeate the family to such an extent that to create a child with him would doom the child (and me) to years of grief from association? If so, then I'm not going to risk a pregnancy. The young woman I mentioned earlier who just had a baby (alcoholic BF who won't give her a cent and gripes about the pregnancy inconveniencing him, etc.) is one of the BEST individuals his family has ever produced.

He is the shining star in a family that defines dysfunction. And now she and that baby are tied to them forever.
(2.) If I got pregnant, would I be proud and happy to marry him and have him as the father of my child and would be feel the same way about me? If the answer is 'no' then I'm not risking a pregnancy. If a man was not that committed to me, I'd want no part of him.
I know the stats. Yes, many marriages end in divorce. But any study will show that fathers of children who were married to the mother (even if they divorced later) are much more involved in the life of the child than fathers who never married the mother. (I'd have to read the studies on those who marry AFTER the birth.) The stats are staggering. Of course, there are those who never marry and stay committed for decades. Look at Goldie Hawn and Kurt Russell. But they are the exception and not the rule. Add up all the pregnant girls you ever knew, divide them into "got married" and "didn't get married" and 10 years later, the "got married"s will have a higher percentage of father/child involvement. Doubtless, what I have seen during the time I was an attorney colored my feelings. But most often, willingness to make a legal committment to the mother translated to making a lasting emotional committment to the child, even when the marriage ended in divorce. This is not an absolute, mind you....simply going with percentages.
Maybe that is part of what we're seeing here. It's not so much, "Only virgins (or faux virgins) are entitled to church weddings," as it is a case of some women being extremely risk averse and having what amounts to a primal desire to make sure their child has economic and legal protection even before birth. Those who carry that a step further and wouldn't have a child with a man they were not prepared to marry would obviously be more than ready to make it official before the child is born. Therefore, the wedding would become insignificant to their perceived need to make the union legally stable and more secure for the child.
I'm
not saying other mothers don't care about the security of their children. I'm saying it may have more to do with the nature of the woman....partly religious, partly whether she's risk averse or not, partly how she was raised, partly.....a lot of different things.