>>724018254
It's important. The reason is actually easy to understand. Fire Emblem has enemy phase combat in which you can consistently retaliate at full power, so it's better to retaliate on as many enemies as possible to cut down on wasted actions cleaning up stragglers in future turns. Since 99% of enemies attack from 1 range or 2, a weapon that retaliates on 99% of enemies is obviously very powerful if you can get it to consistently kill. Doesn't matter if only 10 out of 40 enemies attack with 1-2 or 2-range - that's 25% of enemies you don't have to think about on player phase.
This has always been important in every game, but it's become even more salient in more modern games, where you often suffer penalties by entering combat and failing to one-round the enemy. See: Conquest, Engage.