I do not know, and neither will I claim to understand how knife regulation works in the US, but where I live in my part of the world, it ceases to be their problem and it becomes your problem when knife laws explicitly deem it illegal to carry a knife around without any lawful purpose. Let's be really honest here, many carry a knife on them while actively looking for reasons to use it. Things like "I have a knife on me in case I need to cut open a package" or "I carry a knife to cut my shoelace should it get caught in the escalator" do not constitute lawful purpose under the eyes of the law; law enforcement officers can and will bluntly point out that since you have not received a package and have not had your shoelaces caught in the escalator at the time you were searched / frisked, your knife serves no lawful purpose and it will be automatically assumed to be intended for unlawful usage and you have no defense against it (our laws explicitly state that the inability to prove legitimate and lawful purposes for possession of a knife in public automatically assumes unlawful intent or motivation, regardless of your claims to the contrary). Say hello to the lockup and look forward to have criminal proceedings for weapon possession brought against you.
By the way, where I live the cops also have the right to stop anybody in public and frisk him if they so much as suspect that someone is behaving shadily. I have been stopped and searched and questioned by officers for carrying two screwdrivers and a pair of wirecutters on me. My supervisor had to come down from work to confirm that I have a legitimate purpose to carry them with me at all times (i work in tech support, go figure).
Under such circumstances, to not be extra sensitive about the mindset and stereotypes of the average person is really asking for trouble, especially in an environment. Even the simple act of extracting your knife from your pocket to perform a legitimate cutting task in a public area can constitute unlawful possession of a weapon if the cops receive a call from a paranoid person who happens to be in the vicinity, and you will be detained for questioning. In the end, it all boils down to basic common sense; I'd rather be a wuss and protect my precious rear end.
Lastly, just a point I'd like to make: if the laws and culture in your country or state or town or community or neighborhood or suburb is such that the very first question a friend asks you upon seeing your knife, be it in jest or not, is somewhere along the lines of "Do you know that it's illegal to carry a knife for no reason in public?" or "Who are you going to kill/hurt/stab/cut?", you should really go back home, sit down and think hard about whether your preferences and individuality are worth risking a criminal record for.