My ex-girlfriend was kicked out of her church and disowned by her parents because she admitted to being sexually active. She was a senior in high school. She had to finish the school year living out of her car and relying on friends' charity.
Privacy is a protection against (often irrational) people who are out to hurt you.
There might be reason for people to care about the general fact of "did they have sex?"--but this can be inferred/derived from other sources, e.g. purchasing habits.
How people are having sex, on the other hand, is pretty irrelevant to everyone except those people, isn't it?
The attorney-general of Virginia is seeking to preserve a law that would ban sodomy, which in Virginia includes oral sex. Yes, there are some people who think that how you have sex is very much their business, notwithstanding the fact that they talk out the other side of their mouth about their disdain for big government (I refer here to his arguments against Obamacare).
Privacy is a protection against (often irrational) people who are out to hurt you.