Carrying is one thing, using is another very different thing. So what if a person can carry in NY or IL (for example) - if faced with using a firearm for self-defense, they will still be subject to local laws regarding things like castle doctrine, duty to retreat, etc., and the whims of the local prosecutor. I wouldn't want to be the test case in LA, NYC, or Chicago; would you? I'd love to be able to carry everywhere, but if I can't effectively protect myself, then merely being able to carry is pretty useless.
You are correct, but I'd rather be a test case than dead. Even more important, I'd rather be a test case than have a member of my family dead.
The big thing about this law is just avoiding the legal jeopardy for merely carrying.