They legalise it so that the individual may protect themselves in case they are assaulted, someone enters their property illegally with malicious intent, and other reasons which could justify having a firearm. Many people have never had to use it and they have it as more of a deterrent than anything else. There are of course those who don't use it responsibly and for all the wrong reasons. If strict measures are in place for training to use a firearm and vetting of a person's mental state before being able to purchase one, the chances of a responsible gun owner is likely. Don't forget, the gun can't pull its own trigger.