The reason can only be this: heroic poetry depends on an heroic age, and an age is heroic because of what it is, not because of what it does.
“I had two family members involved in World War I: two great-uncles. One of them is on a memorial in France. And the other was a trench runner who survived the war. The average life span of a trench runner was 36 hours, but he survived the whole war.”
“My doctors warned me repeatedly that if you don't stay positive, you don't do well.”