Why are brass knuckles and other weapons like switchblades illegal?

Now I know brass knuckles are deadly as all hell, but so are guns, tac knives, swords, daggers, grenades, etc. And people can own them and even use some. People also say "well a gun is traceable" and that's true but if u change the barrel before use and don't license it, it is virtually untraceable, people slip up and make rookie mistakes, that's why they get caught. Another point is that anything is a potential weapon, I mean the sky is literally the limit, if someone truly wishes to kill someone they will, weapons just make it quicker, easier and less complicated. People also frequently bring up the point that it has no practical defense application but neither do desert eagles but people own them, people can even own rocket launchers, assault rifles, sub machine guns, shotguns, full blown machine guns, LMGs, sniper rifles capable of taking out small armored vehicles, grenades, the list is endless but god forbid they have a f u c k i n g piece of brass that requires the person to be within 3 feet of the other guy. People but kitchen knife sets with butcher knives the size of full size daggers and just as sharp but why on earth should they have a three inch blade with a plastic handle. A diamond ring actually probably does about half as much damage as a brass knuckle so what if I got three? U can usually recover completely recover from one or two hits by a brass k but one bullet is all it takes and most guns have 10 or more. U can even buy knives so horrific looking they'd be worthy of hell, but those are legal. I just wonder how many more laws we need to save ourselves from ourselves. A f u c k i n g pencil with a rubber band is actually considered a weapon and so is a laser pointer I mean pretty soon u won't be able to walk around with loose change in your pocket. Saying u can obtain pretty much any weapon besides a brass k or a switchblade is about as ridiculous as saying u can legally obtain all drugs with a few exceptions but u can't buy weed.