Marriage is at its core property law that promotes social stability and commitment to a status quo. If you're gay but willing to pay a mortgage, raise a kid, and keep number going up they're happy to have you for the moment. I don't see it as a prize to be won but as a culture war touchpoint that has served its purpose and an option for those with previously subversive lifestyles to give up/buy in.

It's not as appealing or accessible of an option as it once was, and I don't think they can afford to be as picky as they might like. If we get to a point where the Department of Family needs your home for a couple with more traditional values it'll be another story, but I imagine religion, race, and political affiliation (in roughly that order) will be greater risk factors than sexuality. As is, getting married at all is a clear enough signal of alignment to be left alone