It's their culture. They're Independent Fundamentalist Baptists and Quiverfull, which is a Christian Dominionist philosophy. They believe that God gives a man arrows to put in his quiver so that there will be an army to fight the infidels. The ALERT academy that their sons go is training ground for this. Also, this is Christian Patriarchy. A woman's worth is in being a wife and mother. And the more kids, the more value. Here is an analogy: Getting married is like having a high school diploma. Having one child is like having an AA degree. Having 3-6 kids is like having a BA. Having 7-10 is like obtaining a master's degree. Michelle Duggar has a doctorate. Lol. Procreation is what the girls are conditioned and trained to want to do. They have few other options except possibly an online college class, or maybe working in a somewhat sex-segregated job like being a doula, or hairdresser, but only until marriage, and of course working with male family members like brothers, dads and husbands, or sometimes having an online business. They believe birth control causes miscarriages and it is firmly against their religious beliefs. Andrea Yates had the same beliefs.