You're implying that the amount of homosexuality is increasing as a %, that would be impossible to prove.
Some "fake" it because it can help them in professional careerer. Gays, just like any smaller interest group that has been pushed away by majority, tend to stick together and work harder.
Not sure are gays growing in numbers, don't find any relevance in that. Bringing whole matter to biological level is silly, but both sides (homophobes and gays) are using that as a weapon to achieve their goals.
Now you can say it is impossible to change sexual preference or fake it but I disagree. Sexual preference change over time. You might not become bisexual but that's mostly because you're too afraid to even give it a try, not because you're born straight. You're afraid how other will judge you. But when it comes to straight, which is socially acceptable on almost all levels, you change preference all the time. As younger guy you might be into one type of women, later in completely different type. They are not all the same. It's not different as having sex with another gender, but there are differences. Sex has two key components and physical contact and the way how you do it is just one part. The other is attraction and what we call chemistry.
Women are different than men when it comes to this, they like to experiment a lot more. Many women are bisexual and don't find it strange to be with another women. Men are a bit stuck up when it comes to that but I don't blame them. After all, men are the uglier and less desirable gender.