I believe the answer is: The war efforts needed the participation of as many people as possible
Nuclear bombs were never widely used in wars, (their initial usage in hiroshima and nagasaki basically ended the world war ii).
Due to the nature of world war i, most of the battle occured on land, especially near the beach of land borders. Because of this, each countries need as many people as possible to draft as soldiers.
The war efforts needed the participation of as many people as possible.
In a Word War I, all spheres of the society were concentrated on the war effort:
While most of the males fit for the military are sent to battle, the women, as well as the children, also participate in another key "frontlines".
The women in WWI were sent to factories where they started to ignite the production of the economic base. The children also contributed to working in factories and doing other works that would by other means
The role of the woman increased as nurses, holding weapons, constructing warships, Some even like the British royal airforce.
When the death of husbands took place, woman replaced. As well as this, many of them worked in munition industries.
In other countries like Russia, Austria many other civilians offered willingly to volunteer in the war effort.
There is a common will "to sacrifice for everything" society works winning the war.
