Another factor—at least until modern times and probably before as well—is that the present generation is too young to remember the horrors of the previous war.
I remember how reluctant warriors from WWII were to even talk about the unspeakable horrors of war. Then they eventually die off and there is nobody left to remember.
There are so many bloodthirsty pom pom girls cheerleading their chosen team around here you’d think it was a sporting event instead of a war where billions of human beings could die.