"Because they're afraid someone might think they're dancing."

Growing up in a Spanish household in the rural South in the early 60s, I had it drilled into me constantly by my culture (both subliminally and by example) that sex was fun, proper and wholesome, and it was one of the great joys of life. Women were expected to be virtuous and men randy, but everyone was expected to be discreet and careful, not because God would punish you, but because it could dishonor the family. Fathers usually had the duty of explaining the "birds and bees" to sons, mothers explained it to daughters. In both cases the basic education was done at home, well before the onset of puberty.

However, I was also taught that unless sex was properly managed it could lead to all sorts of headaches and problems. Pre marital sex and pregnancy were very rare, and sexual dysfunction after marriage relatively unheard of (at least, no one talked about it!). Adultery and infidelity, as well as divorce were not uncommon (Cubans were never super-Catholic goody two-shoes), but it was usually later in life amongst the middle-aged, not newlyweds.

In the fundamentalist Protestant community around us, sex was simply not discussed, it was evil, it was dirty. People giggled and whispered about it instead. Premarital sex and teen pregnancy was an epidemic, and divorce extremely common. Our cultural prejudice was that the Anglo community was fundamentally hypocritical, but I soon realized the problem had its origin in a culture that feared sex so much it was unwilling to discuss it and could not educate their children about it. As soon as kids were old enough to feel the urge, the religious prohibitions lost their hold because they were patently nonsensical and they leapt into undisciplined experimentation without any other guidance from their culture.

The failure of abstinence training in American society is no surprise to me, it is based on fear, not knowledge. You can't convince people to ignore their normal biological urges with fear. As soon as you question the validity of the religious prhohibitions, you abandon them immediately.

But if you explain to kids in detail what the pitfalls and problems are, without straining their credulity with the fire and brimstone, they will delay their sexual experimentation until they are a bit older, and wiser. They'll be more responsible about sex because it makes good sense, not because it's dirty.