If it weren't, though, who is going to protect the stereotypical stay-at-home mother who put her husband through college and stood by him throughout his career, being there for the kids and him, only to be replaced by a younger model when he hits 50 years old? What standard would there be for child support/spousal support/reasonable distribution of shared property? There are a hundred questions like this, but you get the drift.
Of course, the same questions can be asked of the homosexual relationship, the polygamous relationship, etc. So, that begs the question (which is really the basic, underlying answer to this whole question) - what value does society gain by heterosexual couples that any other form of relationship does not provide?
I agree with your first point. I'm saying that it's impossible to base the validity, potential for success, or benefit to society of a relationship by only considering who is involved in the relationship. (Which is, essentially, the same thing you're saying.) A gay relationship is no more automatically depraved and lustful than a straight marriage is automatically guaranteed to last (as any statistics will show, successful straight marriages are in the minority). It's just that a lot of the arguments on here against gay marriage is that the relationships are not meaningful because they are not lasting. I say, we allow straight divorces, but not gay marriage? We have no laws against adultery aside from accepted moral code, and no one has ever offered an argument suggesting legislation against straight people dating multiple times, or having sex before marriage. I've read your viewpoints on high divorce rates and I know you agree with this point.
I would caution to be a little wary of studies that claim staggering 75% infidelity rates among gay couples - how solid can those records possibly be? First of all, it's not as if they're married (through no fault of their own), so there are probably very few legal records demonstrating breakups of gay couples, whereas there would be for divorces of straight married couples. I'm sure a survey of many straight couples would reveal almost as much messing-around outside of their boyfriend-girlfriend relationships.
And if the infidelity of the relationships is what's troublesome, shouldn't that be a push to allow them marry? When people begin considering their significant other as someone that it is possible to spend their life with permanently, with the full respect accorded by common law, they'd probably take their relatoinships a little more seriously. That's kind of a cause-effect scenario, in my opinion. Society doesn't want to acknowledge these people as anything more than long term sex buddies or friends with benefits, so many of them choose to act accordingly. Straight people already
do behave the same way, both in and out of marriage, and many more of them would if they had no official option for monogamy as well, I believe.
I do somewhat agree with your argument about providing benefits for the married couple described in your scenario. Also, imagine, if you will, a pair of sisters. Let's assume that both are either unmarried or widowed. One sister grows ill and requires live-in care and medical attention, so the other sister officially moves in with her to care for her. Why is the mother described in your scenario more deserving of support and benefits from the government than the caretaker sister just because she's married? Or, say, a single unmarried parent who must care for his or her children? I think it would make more sense to confer those benefits based on perhaps living together, or demonstrating a committed relationship. I mean, there's currently no legal test required for straight couples when they marry asking if they're really in love and if they'll be good parents in order to receive tax benefits.
Of course, hardly all of that can be undone at this point, and institutions such as child support and protections against divorce at this point have to be regulated by law. I just oppose the further grasp of government control over people's nuptials and living arrangements alike.
I'm going to have to partially disagree with your argument that committed heterosexual relationships are responsible for shaping our societies. I think
monogamous relationships are responsible for doing so. After all, our government doesn't confer benefits on married people because they are straight, they do it to reward monogamy. In those times of yore, monogamy, not heterosexuality (after all, men using female prostitutes are hetero), would have been responsible for cutting down on promiscuity, so that men weren't siring hordes of children by different women, allowing for the establishment of families, creating senses of loyalty to communities by encouraging people to stay in the same place with a committed spouse. Of course, the open relationships at the time would all have been hetero because of religious influences, but I don't think it was the heterosexuality that was important as much as the fact that the idea of having as many sexual partners as possible was no longer deemed normal or even acceptable. And in that situation, wouldn't encouraging more people to get married truly be the cornerstone of our society?