In my state, basically any non-gun weapons are banned. You can't own, possess, or transfer a slingshot, knuckle dusters, or any knife that opens with a spring or gravity for example. You're not allowed to possess "martial arts weapons" which is kinda funny since there are martial arts supply stores. You can't carry a knife over a certain length. And there's a kind of general provision for "anything we didn't think of".
I believe it's because such weapons are difficult to trace. You stab someone with a knife, it could be any knife. But if they recover a bullet from a corpse they will be able to link it to a gun that was manufactured and recorded, and they will know who the owner should be. Might be a stolen gun but at least they have something to go on.
It's also ridiculous in that it's pointless to regulate non-firearms: you can do a lot of damage with a screwdriver but those are legal. You can wear metal-plated boots. The blade on an ice skate is legal to carry as long as it's on an ice skate.
Re: Knives. A man with a knife in his hand can close about 20' of distance before a holstered gun can be drawn and aimed. Knives are also very concealable, such that people in a fight often don't know that a knife was involved until they start bleeding, and if you didn't get stabbed you might not realize there was a knife until after the fight is over. Knife disarms are problematic because a knife is dangerous at all angles. A knife improves the wielder's combat effectiveness - in order to perform a disarm you need to be faster and more skilled than he is. And even then it's no guarantee. I do not feel safe doing a knife disarm - but if it's what you gotta do, you try your best.
Surprise is of absolute importance, overcoming even skill and conditioning. Whoever gets injured first is in a bad position and the distraction may be enough to lose him the fight. And that first injury may be painful enough that he loses morale for just long enough for his enemy to seize the kill.
Finally, adrenaline and momentum will allow you to advance and slay your assailant unless he gets a lucky hit somewhere that disables you, or you lose morale, or you succumb to pain. A man can shoot you while the two of you grapple with the gun, but unless you die instantly you have time to dig his eyes from his face and chew into his neck. If you get the gun from him you empty it into him. At that point you know you will die and you want to destroy him for having the nerve to attack you. Perhaps you can fight him off and receive prompt medical treatment and survive. Perhaps the only thing that comes of it is that he won't attack anyone again and his buddies will think twice about carrying on that kind of lifestyle. But if you don't have that mindset, if you see danger and the first thing that comes to mind is something other than tooth and claw, you have no chance.
And I think general martial arts training would be horrible. I don't want everyone else to be better able to fight. Just makes for more potential threats. I want the douchebag who picks a fight with me to be full of himself but without substance.
EDIT: Because of flesh compression a carry-legal knife can reach organs if you stab hard enough. And it'll be able to hit arteries and the face of course. So why aren't they illegal too? It's senseless.