You are missing my point. You don't think that the state has something to do with how sex and being single or marriage is viewed? If 14 is considered the normal age of marriage why wouldn't they think that 14 is the normal age to have sex?
To me, marriage is different than the single state. I can see what you are saying. If a girl can have sex at the age of 14 within marriage, then why not sex while single at the age of 14? So if the girl can perhaps have a baby within marriage, then why not as a single mom? There are cultural considerations and financial reasons. A married girl has a means of support. Cultural norms or standards of behavior dictate behavior. Most people will still consider 14 as being too young in engage in sexual intercourse. There are even laws governing that behavior outside of marriage. Marriage is accepted as a legal institution in which sexual conduct can take place.
So we are back to culturally accepted standards of behavior. Now, it seems to be generally accepted for very young people to have babies even if not married. I know 14/15 year old girls who have babies and are talking about having a second one before they graduate from school. These girls are not married, BTW. So things are changing in our society, and not for the good.