You can use a weapon without firing it. For example, in this video[1] a rioter stole an M4 carbine from a police car. A security guard pointed a pistol and ordered the rioter to drop the weapon. He did. No shots were fired and the police carbine was recovered. Had the security guard not had a gun, I doubt the situation would have ended as harmlessly as it did.
And in other situations pointing a weapon escalates the problem, causing people to respond like their life is in danger - because it is!
Also that example is a funny one to use, because if the police didn't have carbines in their cars people wouldn't be able to steal them, so this whole situation would never had happened in the first place!
Yes, sometimes introducing a gun escalates a situation. Sometimes it de-escalates by forcing compliance.[1] Sometimes it saves people's lives by stopping a threat. My point is that every country on the planet allows some people to carry guns. Different places just draw the line at different levels of screening, training, and places and times in which one can carry a gun.
There's also an issue of path dependency. What works for one country won't work for others. We learned from the war on drugs that banning something doesn't make it go away. There are more guns in the US than people. A lot of people here don't want them to go away. Unless the federal government wants to fight a civil war, Americans will be armed for the foreseeable future.
Several times in my life, I've had men who were bigger and stronger than me use violence against me. When a man tried to stab me in Oakland, I really wish I'd had a gun instead of nothing. When a stranger in San Francisco pushed me to the ground and tried to beat me with his bare hands, I wish I'd had something more effective than pepper spray. There were other occasions that I don't want to get into. As I said in another comment, the police were absolutely useless. They never caught any of these people. I'm certain that after my encounters with them, these violent criminals victimized dozens of others. These things happen so often that many people don't even report them to the cops. Why waste more of your time when you know nothing will come of it? The statistics in the SF bay area are definitely underestimating the magnitude of the problem.
I've seen similar crimes happen to others. A few years ago I watched a man try to kidnap a woman at knifepoint. The woman was powerless and so was I. The only reason he was stopped was because men with guns showed up and ordered the man to drop the knife. He decided he'd rather be in prison than six feet underground.
Now I live in a place that lets law-abiding citizens carry firearms for self-defense (after background checks, training, and fingerprinting). The difference in people's demeanor is night and day. Civilians aren't scared here. Homeless people exist, but they're not aggressive like they are in SF and Oakland. After moving, my girlfriend (a California native and lifelong Democrat) was so shocked by this that she revised her position on guns. She's now learned to shoot and is interested in getting her own concealed carry permit.
1. https://www.youtube.com/watch?v=aVAMUejexa0