You mean they haven't cured gay by the 24th century? Crimeny, after 300 freaking years these people haven't cured bald, haven't cured gay, haven't cured the common cold. FAIL.
That was probably the most homophobic thing I've ever heard on this website. Intelligence fail.
The journal that the psychological community uses to diagnose psychological illness removed homosexuality in 1977, give or take a year. So it's doubtful that Human's in the 21st century "cured" homosexuality. The notion that you can "cure" something that ISN'T dibilitating to one's life is in and of itself a showcase of ignorance. Being gay is natural, it's documented in 500 species on Earth, and observed in over 5,000. There is no way to tell how many people are gay because society for a large part shuns it (less and less nowaday's thank god.) so they are forced to live lies. Or they live lies out of habit.
In any case, there are too many people who are gay, with the number growing mind you, to think it some disease to be cured. It's not contagious, it's not transferrable by any means, and there are no symptoms in the traditional sense. Those are all categories needed to call homosexuality a disease. And before the argument that a lisp, or wearing flamboyant clothing, and being iffeminate are symtoms is even argued, I could easily say that watching sports with your buddies at the bar, wearing a Patriot's jersey, playing rugby, and saying dude a lot are all symptoms of being a straight man. Then again, I've met plenty of gay men who like to say dude a lot and drink beer with his buddies for the superbowl, and iffeminate men who do the same. That's what makes those "symptoms" unreliable.
To say that homosexuality should be cured goes down a dangerous route, the same route that basically includes genocide. It's disgusting.
All that said...
There were undoubtedly, by COMMON sense, gay people in the Star Trek universe. If it's supposed to be a continuation of our universe, then logically there were gay people as there were gays in the 1960's. Sadly, homophobia via the writers, producers, networks, society, and yes even Gene himself, stubbed that away. Even when Star Trek could've done it with Voyager, which was launched in 1995 (a more than okay time to go into it. It's star trek what do people expect of a show that champions equality and rights.), they still didn't. That was a sad sad event.
Even still, there are no gay people in star trek and it's the 21st century.
It would be ridiculous to think that Human's would genetically breed out homosexuality, or that there would even be a "test" for it. Look how society is now...Massachusetts allows gay marriage, Connecticut allows gay marriage, New Hampshire is about to allow gay marriage, and California did allow gay marriage before all those bigots voted. And even now the state has hundreds of lawsuits against it because of the reverse decision, and Connecticut put into their constitution that it would be unconstitutional to even reopen the subject. And, Obama is calling a panel to investigate the legitimacy of don't ask don't tell. It's just not the way society is going, and it's sad Star Trek didn't understand that.
That aside, Voyager was a small ship, and they way people are randomly assigned to ships negates any "statistic", such as the 1:10 ratio. There were either some gays/lesbians/bi's, or none, there was no way to tell because the topic wasn't even covered. Not to mention in the 24th century more and more people could be "out", making our current stats completely void.