1. Defense from foreign governments – Hitler didn’t invade switzerland, the japanese didn’t invade the US, and private citizens helped win the war of 1812.
2. Defense from your own government – government killed 262 million people in the 20th century after enacting gun control laws.
3. Protection from mobs and rioters – Korean business owners defended against the LA riots.
4. Home defense – to prevent people from breaking into your house, pretty obvious
5. Personal defense – outside of the home, prevention from mugging, raping, stabbing, etc.