How did society ever survive for thousands of years without this?
It survived fine - but many, many, many 14- to 17-year olds gave birth every year. Since we've decided that is officially a Bad Thing and passed laws trying to prevent it, it shouldn't be surprising to see this kind of recommendation from an official body of physicians.
Society survived thousands of years because of natural and social consequences for sex and birth outside of marriage.
Now we pay people to have babies they can’t afford to raise and don’t know how to raise.