Nor do they have the need to.
This has NEVER been about marriage rights for homosexuals. Granted there are some homosexuals who want to be married, but the left doesn't actually care about them as anything more than a tool to advance an agenda.
The population control movement began as a way to limit the reproduction of "undesirable" races and classes of people. But eventually the left realized that it could also be used to advance the notion of sex without consequences.
The whole "Free Love" movement wasn't about equality, it was about destroying the traditional family. Today we live in a society where about half of all babies are born out of wedlock, few people even question unmarried people living together. Over half of marriages end in divorce, so even those children who are born to married parents will oftentimes not be raised in a traditional family.
From the mid-1960s until about ten or fifteen years ago, the left said NOTHING about marriage as a desirable institution, their entire agenda was based upon marriage being UNNECESSARY and even demeaning to women. However, they couldn't get people to stop getting married, they hit a roadblock and couldn't get Christians to stop talking about the sanctity of marriage. So, they adopted the homosexual movement and convinced homosexuals (a group that largely bases relationship on the sexual act itself rather than any sort of commitment) to demand marriage "rights." The left IS NOT doing this because they care about homosexuals (they don't care about them any more than they care about the poor, minorities, unions, etc., they are simply another leftist voting block), the left is doing this to devalue and ultimately destroy the institution of marriage for the rest of us.
Well stated.