There was a time when marriage was necessary for the very survival of the family. At least most people believed that to be true and perpetuated the theory. Women were not allowed to make their way independently, and both they and their children needed the financial support of a man.
Having sex before marriage was a risky venture, because it could make a woman less desirable, and an unmarried woman's future was usually bleak. Children produced outside marriage were almost certainly doomed to a low social status and poverty.
Perhaps those archaic realities and the tendency of some people (mostly men) to cling to the strictures of the past have led to such desperate measures as Utah's HB363, a bill rightly vetoed by Gov. Gary Herbert. It would have stupidly elevated ignorance about sexuality to the law of the land. But refusing to instruct young Utahns in the facts about sex, contraception, homosexuality and other realities will not stem the tide of inevitable changes in the social fabric.