Why do you always have a spare tire in your car? Are you afraid that your next trip to the grocery store will result in a flat? Of course not. You always carry the spare because you don't know when one of your tires will go flat.

Likewise with a defensive sidearm. Since the criminal is not going to make an appointment to attack you, to be of any use a defensive weapon must be ready to hand. When you're at a restaurant (or in the parking lot--plenty of folks are assaulted in parking lots) a gun locked in a safe at home will not do you a damn bit of good.