Chastity belts for both male & female until 6 months after they assume and fulfill the responsibilities of adulthood would go a LONG way toward encouraging young people to grow up.
“Why buy the cow (adult responsibility) when the milk (sex, room & board, maybe a little spending money, tuition, etc) is free!”
I know you were sort of joking, but actually that is basically how things used to be for the most part and is in my opinion what drove young people to WANT to grow up and get out of the house at an early age.
A girl didn't want anything to do with a man who wasn't capable of supporting her. A man wouldn't even have thought of asking a girl (even one who loved him back dearly) to marry him unless he was established in a career and capable of taking care of them both and the children to come.