Even though we should have some gun control (the heat some dudes are packing recreationally is just crazy), guns will never be illegal because some might say that there's a lot more things that should be outlawed for potentially killing you.
Why keep marketing and selling fatty foods that clog your arteries and give you irreversible health problems? Why make cigarettes legal if they've been proven to fukk up your organs? Knives, swords, chainsaws? Potential killing machines. Alot of our technologies have been weaponized (electronics, devices that create fire, etc), so what about them?
The bow and arrow and crossbow were some of the first firearms, should these be outlawed too?
Just like any technology, guns have a purpose besides harming and killing other people, but fukkups have made firearms the ugliness that they are today. Sure there's way too much firepower in some guns, but we alos have to look at the user. Also, human nature is way too advanced to just let guns be illegal. If you have the resources and the time, anyone can just make a portable killing machine that can rival any gun. Take away guns, and that new device will take over.
I get your point, and we need to be aware of gun violence, and figure out a way to curb this disturbing trend, but I'm answering your question on why people still have them on their hands and can walk freely with them. This goes beyond the laws and constitution; this is more of an ethics/human nature argument.