Because the larger society has a role to play as well. While you ‘think’ children are not possible, they could happen. Further, by accepting marriage as it is and has been for thousands of years, children remain a key element to the larger societal question and children are our future. The demographic collapse that has already begun in secularized societies that have aborted, contracepted and sodomized themselves free of the ‘burden of children’ is going to be enormously destructive to our way of life and opens the doors for the tribes of Islam. This isn’t about you, your girlfriend, your boyfriend if you want one or your dog/goat/turtle/etc - it is a matter of national survival.
Did you see where I described us as both being in our early 50's? My lady is past menopause. And if that kid can get through my twenty-five year old vasectomy, with all that he's had to get through, we'd name him Houdini. And you'd be celebrating Christmas on a whole 'nother day!
This isn’t about you, your girlfriend, your boyfriend if you want one or your dog/goat/turtle/etc - it is a matter of national survival.
And letting homosexuals marry each other is going to stop straight young people from finding each other, marrying, and having children to perpetuate our society? Or, perhaps you believe that with enough official discouragement of homosexuality, those people will suddenly go straight?
We've tried that, and the most tragic cases I can think of as a result of that misguided attempt to legislate sexual orientation are the straight spouses who are left when their partner decides they really can't go on pretending to be something they're not. McGreevey's wife is just one of the people I have in mind.