Then again it's not like other nations and religious organizations don't share this taboo.
To whit: the popular story about Annie Oakley, the famous lady trick shot and sharp shooter, has her supposedly marrying her husband, Frank E. Butler, at the age of 16. Of course, this matter is contested to this day, with some people putting the marriage several years later.
But no matter which version of the story you ascribe to, the one incontrovertible fact is that when they first met, she was 15 and he was 28 (a difference of 13 years between them - you may now insert the shocked pikachu face here).
Fortunately for our sensibilities, it was real love. They never parted ways, not even really in death. After she passed away, he passed on as well just a few weeks later - he was that devoted to her.
Anyhow, the point is that at some point, very
very recently (that is, from the perspective of human history as a whole), it became absolutely taboo for an adult to have any relations with a teenager beyond what is deemed socially accepted (e.g.: family members and teachers).
I have a number of thoughts about this matter, but it would be better discussed via private messages. Feel free to hit me up.