I don't think hetairoi from Epirus took part in Alexander's campaign against Persia, or in the wars of the Diodochi that followed. Unlike the Macedonians, the Epirotes didn't encounter Persian-style massed foot archers or Skythian horse-archers. So didn't have such a pressing need for anti-arrow armour.

The Epirotes were fighting Illryians, Greeks and Italians who didn't use archery to the same extent as the Asian peoples.