Because barely anybody has a gun, not even the cops carry guns unless they're going to a crime scene where the perpetrator is armed and dangerous.
Thats because there was never a criminal-police arms race there.
This has happened in the US a few times which I have already cited.
Rolling over and handing your wallet to a theif may be acceptable in a lot of places, but in the US we believe a citizen has the right not to hand over his belongings and safety to a criminal. Your criminals dont arm themselves for two reasons:
The police dont carry, so there is no threat of harm in carrying out a crime. The bighest risk is being asked to surrender.
The citizens dont dare defend themselves for fear of legal consequences.
I dont know of any other country with communities which expressly encourage a "stand your ground" mentality.

As long as you are willing to roll over, a criminal will simply take what they like and walk away. The second you defend your right not to be robbed, you are in danger.

Thats the logic.

In the united states, we dont like giving up. We dont like rolling over and letting things happen to us. But even in places which arent as emphatic about self defense tjere is violent crime.
Everyone is familiar with the mexican cartel right?
Columbian geurillas?
Yakuza, palistinian pureists, japanese red army wannabes.

Speaking of which, a japanese terrorist group which claimed to be reminant of the japanese red army got their hands on rocket launchers and small arms and were captured outside yokosuka naval base, planning to fire the rocket at a navy ship.
Guns are illigal in japan.
They had a rocket and they were going to use it. Luckily some of the good ol boys saw a man carrying the rocket near an enterence to the base and subdued him, saving lives of not just US military, but JDSF members and japanese civilians.
Nothing bad had a chance to happen because the sailors who guarded the checkpoint were armed and did not allow the crazies to start firing. Nobody was hurt, not a single shot was fired.
There are police all over that city and at leadt one must have saw him walking around with an RPG, why didnt the japanese police stop him?
Because he was armed and they were not.

Now you know what to think.