Because in real life even a pistol can get a one hit kill.

Guns should be in control of the authorities... There's no good reason anyone should carry a gun with them at all times. "Protection" is bullchocolate, just because someone starts on you does not give you the right to whip out a lethal weapon.

If you should have a gun, it should be no more than a pistol, locked in a box until it is taken to a designated firing area/range.