Gays are the only minority who are often born into families that will reject them. If you're black, Jewish, etc chances are that no matter what other problems you'll face at the least your family will share your minority status and be there to support you and teach you how to cope and survive. Gays often are born into families that are hostile to them and have to figure things out from a young age all on their own.
Man, that sucks.
Though I can think of at least one other minority that faces that same risk of family rejection or misunderstanding -- neuro-atypical people, e.g. people on the autistic spectrum. Many children born with atypical neurology might be misunderstood as unintelligent or misbehaving or "not right" and be badly treated for it. I think ADHD was long perceived as a discipline problem and might've been met with frequent punishment.
And it wasn't so long ago that being left-handed was seen as an intrinsically wrong or evil thing to be, and parents and teachers tried to "train" left-handed people to conform to right-handedness using methods now understood as abusive and damaging.
You see, this is why I like science fiction about the future, especially optimistic SF like
Star Trek. Nostalgia for the past is total BS. The present may not be perfect, but the past was so very much worse.
So with that kind of pressure it's no wonder that some gay people do try to hide in relationships with the opposite sex. It's not just a matter of social standing, it can be seen as survival. I dated women when I was younger, but never more than a couple of dates with the same girl, as I didn't want to let it get serious.
Understandable in the present day, but one hopes that such stigmas would be gone in the 23rd century. This was the crux of George Takei's objection to the idea of Sulu being gay -- because he felt it implied that his Sulu had been closeted, which in turn implied that homophobia was still around in the future. Although as I've said, I don't think that really follows from the sparse evidence TOS provides. (Someone pointed out to me on my blog this morning that even
The Captain's Daughter shows Sulu's fling with Susan as a one-night stand with an exceptional woman, and thus doesn't necessarily prove anything about his normal preferences.)
Having grown up without gay role models, I can say that having a positive gay character on Trek would've been a huge boost for me then. Now there are gay characters out there, even if usually in small roles and still underrepresented. It's a shame Trek had to wait until all risk for virtually gone before finally having a gay character on screen, but I'm still thrilled that we've finally gotten here.
Yeah, the franchise really dropped the ball there. Something like "Rejoined" was still fairly daring when they did it -- daring enough that some local stations actually smash-cut to commercial rather than showing two women kissing -- but the fact that they made no effort to push the envelope farther in the ensuing ten years of the televised franchise, even while so many others around them were beating them to it, was a grave disappointment.