..... And secondly, while I personally have not been in a marriage (which I hope will not be put against me), it is logical to recognize an official monogamous relationship since that is what is needed for procreation.
Technically it's not needed as procreation occurs with or without an official monogamous relationship..... if it was indeed needed then that'd be a real sweet form of birth control for most people if it'd simply turn on/off your reproductive abilities based on if the state recognized your relationship as monogamous.
Putting aside gay marriage, since it is already legal, a man and a woman is what is needed for a relationship to prosper into a family. Divorce rates are staggeringly high because individuals do not treat marriage as such, which is the root of the problem. We do need to recognize this as a problem, and not amend our laws to it by changing marriage legislature.
Believe it or not, but my and my siblings lives were a hell of a lot better off after my parents divorced since it eventually stopped them from constantly fighting with one another.... in fact most of the people I have known and talked to over the years who came from broken homes (divorced parents) were glad they broke up and decided to finally go and do what they wanted to do with their lives..... Happy parents mean happy children. Forcing or otherwise pressuring parents to remain together just for the sake of calling their family "Functional" due to having both the father and mother under the same roof is ignorant and short sighted.
It's not just damaging to the parents, but it's even more damaging to the children who have to live in such a stressful and dysfunctional environment and some of those children can grow up thinking that's was marriage is supposed to be like.
Just because my parents no longer lived together or loved each other, doesn't mean I never got to see one or the other ever again or that somehow my life got even worse..... that's an old fashion point of view on divorce. Growing up, I was in one of the last generations where it was commonly thought that children would make fun of you or treat you differently because your parents weren't together.
In fact, there were plenty in my school who were in that situation, and seemed a hell of a lot better off then those in families that fought all the time and only stayed together for the sake of having both parents under the same roof.
After my parents divorced, they go their own places, lived where each wanted to live, they finally got to live their lives as they wanted to, and gradually found relationships that worked for them. My father has since remarried and my mother is common law with her boyfriend of close to 10 years now I suppose. They are happier then I ever remember them to be growing up.
If you really want to know the Real Root of the problem, it has to do with people thinking exactly as you suggest..... that a marriage is needed for a successful and happy family. If you go into a marriage thinking this way and that is, for the most part, the only real reason why you're getting married, then don't expect your marriage to last very long and when it fails, that will be the moment you realize that marriage is a great deal more then this and that getting married isn't some quick fix solution to having a successful marriage.
Two of my friends have children from previous marriages whom eventually divorced from those relationships, found each other, moved in with one another, had another child together and have yet to marry.... whom have been in their current relationship for close to 7 or 8 years now..... they're perfectly happy, their children are happy and one of the reasons why I believe their relationship is successful is because they're doing what they feel is right for their children and are not jumping into any decisions based on old fashion misconceptions of a "happy family"
They already married and know what it's all about..... they have the first hand experience of what happens when you marry based on what you believe above and know that it is far better for them and their children to take their time and do things when they feel the time is right, rather then jumping head first into something that is no quick fix solution.
The moment people stop thinking of marriage as some status factor for having a happy family will also be the moment you see divorce rates drop.
Being married doesn't mean your children are going to be automatically happy, it does not mean you and your significant other are going to suddenly never have any fights, it does not mean all your problems as boy/girlfriend will suddenly be solved, it does not mean that once you're married, you or your significant other are going to change your ways for the better, it does not mean once you're married everything is going to turn into some magical make believe world of fantasy and joy and all your problems are going to be solved...... and if you believe marriage will do any of the above, then your marriage is most likely doomed to fail before it begins because you are marrying for all the wrong reasons.