Probably one of the main questions--right next to "How do we stop dominionists?"--I'm asked when writing is "Why do into coercive religious groups in the first place?"
One thing to note is that, in general, people less join a coercive group and more are recruited into a coercive group or are raised in a coercive group.
A new article by Jonathan Rice and Vyckie Garrison--the latter of whom runs No Longer Quivering, a support forum for ex-Quiverfull survivors--gives a glimpse of how coercive group recruitment works from a first-hand view.