[quote=Hillbilly12]
I know I was just give my theory on the in verse reasoning for not making more mechanical soldiers. They don't seem to explain much in the anime, so I'm making some assumptions. There is one thing in the anime that confused the hell out of me. Why aren't the civil security service a mainly government organization instead of it basically consisting of private contractors? They might explain a bit later.
[/quote]

I had the assumption that the government is tight on cash and resources so its easier this way rather than doing it themselves? 
And I agree that I think they stopped making mechanical soldiers and started using the cursed children because they are less expensive, easier to train, more powerful and are more easily controlled.