Difference there Psion is a great deal of people who are opposed to same-gender marriages in the states also shun video games in general so they wouldn't play it unless it was wholly educational and non-religious to begin with. I can't really speak for Japan on that of course. But look, the entire point of my post was to try offering insight as to likely why they aren't leaping at this chance. Same-sex marriages are a minority and a smaller feature compared to the rest they're focusing on. Besides, correct me if I'm wrong but don't they take things like marriage in online games much more serious than western audiences?
These kind of features exist so two couples in real life can get married in both worlds. I know there have been real instances where people have hosted an online wedding in a video game to say their vows making them legally married in real life, too. So that's even more of a reason for them to be hesitant on it.
The whole point of it is they may add it, they may not. I'm not trying to justify reasons not to introduce it. I'm a male gamer even if I play a Miqo'te and being a RPer too I'd likely have her marry a male character if I so decide. But in the event I do decide otherwise to marry a female character I'd love to have that option available as well so I really do fully support the idea.