the general lack of such previously, as the psy issues of war are a keystone, you cannot have your populace fall to war fatigue. Also why militaries like wounding people more than killing them, so Ma and Pa can see what their war hath wraught when Sonny Boy comes home without legs. Also it costs

more blah blah blah. So it was a new phenom. AND people felt at that time they could trust images and what they saw on the telly more than what was in the papers or said by politicians. In modernity, not so much. But again, I don't know how accurate that is.