That's because they don't. The reasons you listed above would maybe show some kind of dent in the number of guns 100 years from now, but the direction this country is going, where no one wants to budge on their stances, we have religious extremists, heroin addicts robbing more and more houses, and homophobic murderers on the loose shooting people just because they like other dudes, people will want their guns.
The day I hand in my gun is the day all the illegal guns are off the street. When I feel like I won't need it anymore and I can get by with just a melee weapon. Hell, wait a minute, no....now that I think of it, someone comes charging at me with a baseball bat, they would have to be hit center mass too(unless they on some Genji shit), you can't expect me to take a melee weapon to face. This isn't game of thrones