I think that it is really peculiar that we all eat food and it is a major topic, we drink spirits and that too is a major topic. But a function that is responsible for the continued existence of not just humankind but all life on the planet, something that is practised by everyone, excepting those unable or those who by vows of celibacy abstain, is considered taboo to talk about by many.
In these days where almost every problem we face is the result of overpopulation pressure, sex is still a verboten subject. It is like the elephant in the room nobody wants to admit they see. People think their sex life is some kind of sacred cow, like what they do sexually is so unique compared to everybody else that they refuse to talk about it on the grounds that it is "too personal". Well, let clue you in on something: we all do it pretty much the same, just like we all eat pretty much the same and we all defecate pretty much the same.
So why all the secrecy about some peoples sex lives? I'll posit a theory or two. First, I think that people who are reluctant to talk about it either are still laboring under the culturally inculcated idea that sex is "dirty" or "nasty" or even "sacred" at the other end of the spectrum, or they fear that they are inadequate compared to others and don't want to reveal that, or that they are "perverted" and definately don't want people finding that out.
Well let me reiterate: Whoever you are, your sex life isn't special or sacred or dirty or perverted or inadequate. It just is what it is, and if you can't or don't want to talk about it, you need to look deeper. It is a basic biological function and as such doesn't deserve to be relegated to any level other than that, neither "sacred" nor "dirty". The sooner we as a species come to accept all our biological functions, and be able to discuss them in a mature thoughtful manner, the sooner we will come to realize our true role in the ecosystem and act accordingly to bring about a better world.
Communication, true and honest communication is the key to peace and harmony.