One does not need a reason to have guns. The Constitution REQUIRES that citizens have the ability to keep and carry firearms. On the other hand, the Constitution does not require that citizens have the ability to possess automobiles, which kill more people every year than firearms. As to why have them, perhaps if someone had a gun in Connecticut, then fewer children would have died. Following your logic, police should be disarmed also, as well as bodyguards etc because, after all, according to you, possession of a firearm does NOT prevent unlawful violence .