Unfortunately I don't have that interesting of a motive. This really came up from reading Will and Ariel Durant's Dual Autobiography. Durant has been a mild idol of mine for a while, and is one of the few writers/historians I enjoy returning to again and again - but I was relatively shocked when I found out that he, 27, fell in love with Ariel when she was a student of his - at 14. That sort of thing struck me as insane, but the last thing I want to do is to go into the absurdity I felt.
Of course, certainly this is still a custom in parts of the world, and, naturally, they were different times - but I'd like to understand it better to try and understand Durant a little better - I suppose that could be my thesis - I'd just like a bit more perspective.
I apologize that this was such a difficult thing to phrase. I'm not trying to point the fact out as some terrible thing - again, I'd just like to understand the customs better. This post may even be a knee-jerk response, that there might not be much more perspective to gain than "different times, different cultures." Still, I'd be curious if anyone has something to offer. Thanks in advance!
Notice the history of romance novels. Volumes from the 1960s and 1970s, whether contemporary or historical, considered it fairly normal for the hero to be 8-12 years older than the heroine. In short, she would be about twenty while he was thirty. Or older.
It used to be considered quite normal, even desirable. He was ready to settle down and had the wherewithal to support a wife.
EDIT: Even now, romance novels aimed at the European rather than North American market prefer a heroine in her early twenties, or younger, and a hero in his thirties.
Any biography of someone like Henry VIII. He was almost 50 when he married Catherine Howard who was 18/19. It was pretty normal in the middle ages for men to marry young (barely teenagers) women. Henry III has a very young wife- 13 or so I think. Death in childbirth was common and if you wanted an heir, you needed a young wife.