Quantity has quality of it's own. If the weapon has Pk ratio just 0.01 and you launch 300 of them, the probability that at least one gets trough is 0.95. More

Quantity has quality of it's own. If the weapon has Pk ratio just 0.01 and you launch 300 of them, the probability that at least one gets trough is 0.95. More importantly weapons in naval ships have limited magazine sizes. Once they run out, they are nothing but targets. More you add defensive weapons into limited number of canisters, less you have left for offensive weapons.