Yes, and also just as scarcely any a robber wants to become a murderer, similarly people will shy away from violence against kids.
Both for moral reasons, but also because the penalties are tougher.
(And not just the legal penalties. I would assume you also run a higher risk of a bystander rushing in and becoming hero. And of your prison mates later ganging up on you. People _love_ children, not just their own, and many would gladly give their lives for them.)
