I've had that thought about my own Evangelical past—that parents can oddly enjoy the idea of religiously sacrificing the child.

I think the key to Protestantism in general is that, leaving Catholicism, it was never clear how to "do" the Bible, i.e. how establish oneself as good and God's favorite people.

The idea naturally arose doing the most horrifying thing one could imagine, child sacrifice, as a proof of devotion. Women are so often prompted to pray Hannah's prayer—as if the price of the child they want will be that they must give it up.