The element of surprise.
Because no one knows you’re carrying, if you do need to use your handgun for self-defense, you will probably have the element of surprise. When criminals are targeting people, they’re generally looking to avoid actual violent confrontation because that means the potential for injury and needing to seek medical attention. If they’re so bold as to move against you, your family, or your property, they will be in for a severe surprise because you’re carrying a concealed handgun.