The use of women, children and immigrant allowed industrialists and factory owners to keep wages low for native born men. This was an important catalyst for the organization of labor unions, Children often worked long hours for low pay. The same was true of women and immigrants.
They were hindered by economic development and lack of enforcement, so I'd say 1. Cost, because no one would pay for it.
Answer:
A.) France, Russia, U.S, and Britain
The US did complain, a lot. Mostly due to that fact that Western Berlin which was controlled By the USA, France and Britian was securely behind this barrier and so to supply half of an entire city they had to fly in 24/7 airlift cargo missions for weeks on end to keep the city from starving.
