I'd have guessed that teenagers dont have enough places where theyre unsupervised or otherwise surveiled such that they can have sex without thinking about the possible results of said sex.

"its the advertising" could be another one. people today are put on a heavy track with very high expectation about everything that needs to be done before even considering parenthood - same thing as with the trades. everyone is trained to think being a parent before getting other accomplishments makes you a failure