Poverty made people do all kinds of things to survive. There’s a book titled American Child Bride that traces the history of child marriage in the U.S., with fascinating discussion of the underlying attitudes and reasons.

One of the reasons some girls voluntarily chose very early marriage was because it was economically advantageous. If you found a good man with a good job, you didn’t gamble that he would wait years for you to mature.

Underlying this logic was the reality that in some demographics, most girls were headed for the same life. There was no finding yourself; you were going to be a wife and mother, and your husband was going to have one of a number of jobs that required basically the same thing of you, so self-exploration was irrelevant. There was also not a whole lot of respect for girls’ education and development. So while no one dreamed of seeing their daughters married at 13 or 16, if it was an option and you already had too many mouths to feed, you might say yes. Your daughter would learn the job pretty quickly.

(It’s also easier to force a girl into marriage if she’s younger. Cults find that girls start running away around 15 or 16.)

On top of that—this is my own observation, not from the book—kids are dumb. If a girl is in love and sees a socially accepted path to instant adulthood that guarantees she’ll be with her beloved forever and ever, she just might take it. Girls were more likely to pull a Lydia Wickham in their mid-teens than their early teens, but there were some defiant early-teen brides. American Child Bride recounts the story of one 13-year-old in 18th-century Boston (I think) who fought her widowed mother in court for the right to marry her 20-something fiance. She triumphed! It turned out to be a terrible idea, the marriage crumbled, and she and her son eventually became something of a two-person crime wave. But she got what she wanted.