If we are to trust the evidence of the records it is due to differences in the ideas which animated heroic and non-heroic society.
1540s, shortened from heroical (early 15c.), also heroycus "noble, magnanimous," from Latin heroicus "of a hero, heroic, mythical," from Greek heroikos "pertaining to heroes," from heros (see hero (n.1)). Earlier was heroical (early 15c.). The Heroic Age in Greece was the time before the return of the armies from the fall of Troy. Related: Heroically. Heroic verse (1610s), decasyllabic iambic, is from Italian.
heroic he·ro·ic (hĭ-rō'ĭk)
Relating to a risky medical procedure that may endanger the patient but also has a possibility of being successful, whereas lesser action would result in failure.