To go a bit more into detail, a knife is up close and personal. You have to be in someones face to use it. A big tough thug isn`t afraid of jumping you and cutting you up. (Does that sound like intent to anyone?)
But a gun is a distance weapon that a weaker person ( Small stature, elderly, female, handicapped, take your pick) can use to save their lives. Remember Col. Sam colt made all men equal. The first Colt 6 shooters were even called "Peace Makers">