Why the Need to Come out the Closet?

I just read an article about a 14 year old boy who committed suicide because he was being bullied at school for being bisexual and having all female friends. I do not condone that behavior bullying is wrong no matter what and it is so sad that young people are taking their lives because of it. But in response to his suicide a celebrity, Zachary Quinto, came out of the closet and admitted he was gay. My position is not to argue rather your are born gay or choose to be gay. I am baffled of why, gays, lesbians etc. feel the need to share with the public what they do in private? I am a heterosexual female and I do not tell anyone what I do behind close doors and I believe as long as your are an adult and everyone consents its nobody business what goes on in your bedroom. My thing is that most people make the choice to expose their own sexual orientation, which makes no sense to me. I would have never known that most people are gay if they didn't tell. I know that some people are open about their sexual orientation and I applaud their confidence in who they are. But, the people where no one knew before the fact and tell it would appear as if they are taking a risk and putting a target on their backs. As I stated before this should be a private matter. I get that you feel like you are not being real or true to yourself, but people do it all the time. EVERYONE acts different in public than what they do in the privacy of their own home. So why make the choice to tell it to the world and maybe subject yourself to harm? You should just live your life as you want and the best way to make sure you are happy and not everyone else. Just a thought. What do you think?