Stephen, thanks for sharing that piece. It made me laugh and it brings out a good point about the dangers of tampering with the definiton of marriage.
Christopher, I think that the legal benefits that are found within marriage are there because it was recognized that it was in society's best interest to encourage people in a lifelong commitment of fidelity, of mutual caretaking of each other and of any children that they might produce together. I also agree with the statement in one of the articles that Stephen gave that it was designed in part to protect the women and children of a society in light of the greater tendency in the male of the species to tend toward promiscuity and wandering (not that women haven't or don't, but the tendency toward it is higher in males, statistically), a way to hold them accountable to their responsibilities to their partner and children so that they would not eventually become a burden on society to have to support. Society simply doesn't have a vested interest in encouraging non-marital cohabitation, in my opinion, and therefore doesn't offer any benefits to encourage it.
I believe, and I think all the research bears it out, that in homes where there is this sense of 'till death do us part' in the mother/father relationship, the couple benefits, the children benefit and society benefits, as contrasted with the mindset of semi-commited non-marital cohabitation, keeping all options open, which makes it easier, psychologically and financially, to forsake one's partner and children when the going gets rough.
I think one of the biggest problems in our society since the sexual revolution has been the fostering of the idea of sex and children outside of marriage, with families headed by single women who have no male support, and with children who have no male role model to bond with, which deprives them of an important ingredient to their sense of 'self', and many of those households are mired in poverty because of it. That life is hard on them and hard on society (who has to support them in the majority of the cases, and at a subsistance level compared to average income level homes). The men who have fathered all these children just aren't around physically, and are not supporting their children financially in most cases. So society has to pick up the tab. So everybody loses, including the fathers who never learn to accept their responsibilities, but continue from one woman to the next fathering even more chldren that they do not intend to take care of. And if you think I am exaggerating, come visit my neighborhood. Out of 22 houses on my block alone, there are only 3 households (mine being one) that are not single parent, welfare supported, households. Surely anyone can see the burden created for society in such situations.
I think it is ironic that the movement spearheaded by NOW and the radical feminists in the late sixties and early seventies, purportedly to empower and liberate women, has had just the opposite effect and in many cases has given women an inferior quality of life than they could have had, had they waited for or insisted upon marriage before having children. When they bought into the concept of 'free love' they paid a very dear price, in my opinion.
I think that everything that we do individually affects society in one way or another, eventually, for good or for ill, at least in my opinion.