Some people want world peace and denuclearization. Each country is currently as it finds itself and takes a great deal of leadership and buy-in to change.
That’s not the real world. Criminals will always find a way to get guns no matter the amount of gun control you impose, so I’d rather have law abiding citizens be armed as well
It is the real world in many places. "Criminals" are not a homogenous group. Petty criminals will not usually be making the effort to get a gun if getting a gun is inconvenient. Some high level criminals will find ways to get guns but the number of criminals with guns will be much lower with gun controls.
It’s not your real world, lots of other countries have so little gun violence that a shooting makes the national news when it happens and thats maybe once or twice a year.
There are countries in the EU which have pretty lax gun laws and firefighters are fairly accessible they still have fairly low levels of gun crime. Just having access to weapons doesn’t mean that people will start killing each other for no reason, there are many other more important factors.