By your metrics, the most lethal thing in the world is a rusty spoon stabbed into some ones eye; either it kills the target instantly or kills them later due to infection. Very close to 100% death rate. Very lethal. No collateral damages, either.
And yet no professional militaries are armed with rusty spoons
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.
They had swords that did that. Then they found out that guns had higher lethality with lower risk to the attacker (another primary metric). Collateral wasn't much of a problem back then. No one gave a shit.
By your metrics, the most lethal thing in the world is a rusty spoon stabbed into some ones eye; either it kills the target instantly or kills them later due to infection. Very close to 100% death rate. Very lethal. No collateral damages, either.
And yet no professional militaries are armed with rusty spoons