I think, Gay story or not, some sex scene can be a good way to spice it up in a story, specially if it is a romance (let's not speak about eroticas which revolve around sex). I do write a lot of gay sex scenes, but I involve emotions to it, maybe because I believe that people give in more when they are drunk by lust. It's a perception of mine, nothing to do with real life.
I like sex scenes when they are making the story look more credible. I mean a couple who live in the same house for months have to have sex at least 4 times a week. As well, there a studies saying that the happiest couples have sex more often... if real people appreciate intimate moments, out of nowhere, with their partner why should our stories exclude it?
However, that exclude the cases where the both characters aren't living together or deny their emotions for each other (it will be hella of awkward if they had sex that often...)