Gun ownership doesn't help public safety anywhere near as much as you think.
The number one and number two uses of guns inside a home are suicide and murder of a loved one, respectively. Defending against a home invader is statistically uncommon at best. But people get angry every day, and we all have moments of weakness and vulnerability.
To your point about criminals, have you ever been robbed? A robber isn't going to announce his intentions from 20 feet away.
Does having a gun under your shirt help you if somebody pokes a knife into your back? Maybe you could draw and murder them in revenge as they leave I guess.
I know that gun-safety classes are mandatory for any kind of concealed-carry permit. But I can 100% guarantee that they don't prepare you for the psychological reality of killing somebody.
And let's say you actually find yourself in a situation where drawing your gun makes it better instead of worse - do you use it? If so, prepare yourself to pay every dime you have to a defense attorney, and to give up a year of your life to court proceedings. Even in a stand-your-ground state. And that's assuming you don't miss and hit somebody else by mistake.
Human-nature is to stand by and watch when something bad goes down. Carrying a gun doesn't change that. And a three-day course on gun safety doesn't prepare you for the reality of drawing on a human and firing.
On the other side of the argument - when guns are easy to buy, lots of people buy them legally. Then some of those people have them stolen or sell them. And others resell them.
When guns are cheap and cheerful, it's easy for a criminal to get one. When guns are expensive and hard-to-get, some criminals might still get one. But a lot of other criminals won't go through the effort. Why find an illegal gun dealer when you can buy a kitchen knife at Costco? And believe it or not - that's a big win for overall public safety.
Also if we could get guns out of the hands of the general population, we'd be able to make a better case for de-militarizing our police. And that would be a _huge_ win for public safety.
The US's founders weren't gods, and they didn't have a crystal ball into the future. We shouldn't treat their words as some kind of immortal and perfect document, to be interpreted on a word-by-word basis like bible scholars. And when the US was founded, the common gun needed a ramrod to load the single shot it carried.