That's because the lethality of a rusty spoon is actually very low... The lethality of having been stabbed in the eye might be high, but not of spoons themselves since it is hard to successfully wound the eye of an enemy soldier with a rusty spoon at a distance when said enemy soldier is armed with ranged weaponry, and it is still difficult to do even in melee range relative to how easy it is to wound with bayonets and combat knives.