At least you are open to an opt out!
You mean make a dead-beat dad the expected norm, and have to sign a document declaring that you are "out of the norm?"
Well, because the state gets involved in child support enforcement, and for tax purposes. If has has that kind of bond with the child, and still wants to be a dad/father figure, why make it more difficult for him to do so? What if he wants to be an emergency contact for the children? What if he is needed to make an emergency decision on behalf of the child in case of a medical emergency? Are people such as this actually that rare? Say it isn't so!