Prussia was also a highly militaristic state, so it had the side benefit of keeping the young men fit and hearty enough to get conscripted for the next time they needed to bloody France's nose. It would also have the young women fit enough to bear many much young men that they could conscript into future wars.

The logic of trench warfare era militarism is even more depressing than the normal logic of war. It's mind-boggling to think leaders figured it was appropriate to just throw demographically significant numbers of 16-20 year old boys into a meat-grinder just to keep the machinery of colonialist industry well greased.