Nobody cares why a thing was designed, or its intended purpose, except as to weapons.
I was really hoping someone would bring this up. As far as weapons killing people goes, it would not be too implausible to say that modern day weapons are designed for the purposes of hunting, sporting, or self-defense.
Even military arms, like my M16, have a design criteria centered around keeping me, the user, safe. If I am on the defensive, I want to know that my rifle will shoot every time I pull the trigger and that it will hit where I am aiming. Even if I am on the offensive, a weapon that is accurate and reliable is a weapon that is keeping me alive. Commanders care a lot more about keeping their men alive than they do about killing other men.
Obviously someone who commits a crime with a civilian model firearm is not using the weapon for its intended purpose anymore than someone who drinks and drives is using alcohol for its intended purpose.