There is another reason. In social-standing friendly language, "Sex is sacred".

For the less socially-friendly approach... sex is clearly not sacred, and the issue isn't the idea of sex being a right, as one can readily see by looking at people who can complain about involuntary celibacy without much social risk, and do so. I'm not going to name the ugliness, both because it's broad and ill-defined - a patch of area defined more by what a set of ideologies fail to say, than what they explicitly name - but also because it's something you have to see for yourself to believe.