Conservative and traditional models for starting families are poorly adapted for the modern environment where the ability to manipulate complex streams of information translates to earning power and knowledge equals power.
But then along come two game-changers: the global information economy and the birth-control revolution. The postindustrial economy puts a premium on skill and cognitive ability. A high school education or less no longer offers very good prospects. Blue-collar wages fall, so a factory job no longer cuts it -- if, that is, you can even find a factory job.
Meanwhile, birth control separates decisions about sex from decisions about parenthood, and the advent of effective female contraception lets men shift the moral responsibility for pregnancy to women, eroding the shotgun marriage. Divorce becomes easy to obtain and sheds its stigma. Women stream into the workforce and become more economically independent -- a good thing, but with the side effect of contributing to a much higher divorce rate.
In this very different world, early family formation is often a calamity. It short-circuits skill acquisition by knocking one or both parents out of school. It carries a high penalty for immature marital judgment in the form of likely divorce. It leaves many young mothers, now bearing both the children and the cultural responsibility for pregnancy, without the option of ever marrying at all.
New norms arise for this environment, norms geared to prevent premature family formation. The new paradigm prizes responsible childbearing and child-rearing far above the traditional linkage of sex, marriage, and procreation. Instead of emphasizing abstinence until marriage, it enjoins: Don't form a family until after you have finished your education and are equipped for responsibility. In other words, adults form families. Family life marks the end of the transition to adulthood, not the beginning.