My anecdotal experience has been that the older generations of gay men haven't cared a lot about gay marriage as an issue. Civil unions give them what they needed legally, and "marriage" as a concept separate from that didn't mean much to them.

I'm completely theorizing as to why, but it's a topic I've discussed with many of them and thought about some on my own.

The following impressions apply to older gay men I've met who don't care much about gay marriage as an issue. I'm explicitly stating I don't believe they necessarily apply to a wider gay community.

I think part of it is that older gay men tend to have been in some longer, more committed relationships, and feel that the reality of day to day loving is what matters to them. Give them legal rights with civil unions and they're good to go. They don't need "marriage" to feel more committed.

I think too older men are more comfortable with themselves and who they are. They have been gay and out (at least to some close friends, if no one else) for long periods of time and don't feel as much shame or need to be "accepted" by everyone. So the symbolic meaning of gay marriage (as opposed to civil unions) carries less weight for them.

And related, they've seen the truly big battles that were fought for the right to be out at all. This one feels smaller to them, less essential in comparison. They're happy with what they have. It's all they feel they need.