While there is plenty of room for endless musings on the legal and religious basis for marriage, I think I'll just talk from personal experience.
I was married for 20 years to a woman that, in the end, I found I couldn't tolerate. After separating, I still found myself with an inate yearning to be a family man. I was able to spend this time feeling this desire and getting a grip on it. After separation I felt a poingniant sense of loss of identity. I identified myself for 20 years as a husband, dad, provider, protector, lover, and playmate for the people in my family. I found myself feeling that, while I had a resonably strong sense of personal identity, I had little outlet for my desires to be close with others and serve them. Essentially, as a batchelor, I found that I would retreat into self-serving behaviours due to a lack of other outlets. It was far easier to serve myself and my time wasn't dictated by the needs of a family, but I also felt a certain uselessness to my existance. It became obvious to me that it was far more deeply satisfying to suffer the needs of others and serve them, than to simply satisfy ones own desires. I recall this relativly short time as being quite dark.
So I started searching for a mate. I was particularly interested in finding a divorced woman with children as I felt I loved being a dad. I got lucky and found one: Beth, and her two boys Chance (now 14) and Liam (now 10). I also have a daughter April (now 10) who I ended up having custody of.
I am now happily married. While we had a bit of a rough road for the first year (evidently very typical in a second marriage) we've been very happy this second year and the home is running on all 12 cylinders.
I tend to think the desire for marriage is much deeper than societal (legal), or cultural (peer pressure so to speak) norms. It seems to me as I think about it for myself, that it has to do more with being a part of a tribe. In this day and age in America, society and culture are pretty impersonal. I think what I was looking for was belonging to a tightly knit group of people in which to have personal relationships, and to provide personal help to others. Because of my cultural background, that meant a marriage. So, I don't think procreation per se was the motive---although child rearing was---as much as it was finding a place for intimate relations.
As an interesting aside, my family now has a very unusual set of not blood related relatives. Chance's dad is not his biological dad. The kids have a grand dad that is not biologically related. And the list goes on. So, we are in this odd environment of having adopted a large part of the extended family, as well as the whole step-mom, step-dad, step-brother, and step-sister thing. I can assure you that the love and caring among these people is much stronger than in my preiously biologically entact family.
A couple of notes:
Belonging and participating in a family well include the ability to suffer others gladly. It's much easier to find pleasure alone. But not truly satisfying pleasure---at least for me.
Even though I think it was better for me and my children (my ex still suffers, and IMO due to her selfish nature), I think my seperation and divorce was the most painful experience of my life. The view of divorce as an abomination has great truth.
And therefor, just because you suffer, doesn't mean divorce is the right answer. I suffered for 20 years before I fled. Every time I wanted to choose divorce, I decided against it. When I finally left it didn't feel like a choice, it was more a flight for survival. If I had to do it again knowing what I know now, I would probably do the same thing. That may sound pretty stupid, but I have to tell you that there is almost no way of knowing if you'll truly get along with your mate untill you're years down the road.
If I had to choose a mate today, I would probably try eHarmony. I tend to think that issues of every day compatability are very important. You may think you love somebody now, but if they don't replace the toilet paper and you're a bit obsessive compulsive, that's going to be bothersome and may escelate over the years. Marriage is somewhat more about living in a comfortable home together than sex or love. Personally, I love people, and have therefor come to believe I could marry most any girl for love. But I don't think I could live with almost any girl unless our lifestyles matched significantly. Some of my favorite times with my wife are watching the Daily Show or some liberal documentary. I'm sure that would be far less enjoyable with a conservative wife. So issues of personal taste are very important to my mind.
Marriage is much more about warm, comfy slippers, than about hot monkey sex---IMHO.
