I think marriage does make a difference. I have a lot of friends who have never got married, the majority in fact. I certainly don't feel superior in any way - they are entitled to free choice of how they live their lives.
But there is something about marriage, despite the divorce rate. Married people declare to each other that this is a bond for life. Now I am not saying that you can't be committed without marriage, because clearly you can - many of the people posting here are.
Nor am I saying that marriage is a guarantee of staying together - the divorce rate is testament to that. However, I suspect that it is easier to break the bonds if you aren't married. Any long term relationship is going to hit rough patches, and there are going to be real tests on staying together. But I can describe the difference personally for me when I got married, there was an acknowledgement that the ability to walk out of the door simply wasn't there in the same way as it had been before (for both partners).
I have done both cohabiting and marriage, and I think that the piece of paper does make a difference.
More than any of the above, all of which I accept is anecdotal, I believe that the benefits system (which through tax credits now captures a large proportion of the working population as well as unemployed) is biased against people who are married. If you are anywhere near the income thresholds, you are really better keeping your options open and not getting married.
I have seen many of my friends caught in this "trap" and unable to get married for fear of losing the flexibility to claim benefits if needed, housing help and support in the case of temporary separation or job/income insecurity.
In my opinion, it creates a climate of instability in lower income households, which is not in the long term interests of the families concerned. Bugger society I am afraid, it's the families and children themselves I am concerned for.
I don't know what the answer is, but I think to actively discourage marriage, in the way the income tax and benefit systems do at the moment, is wrong for families.
If this is what the Tories are on about, then I accept it. If it is just a meaningless tirade aimed at winning votes in Middle England then I want none of it.