I’d bet the vast majority of it is simply forgetting that the weapon is in their carry on, which tends to be a commonly carried piece of equipment anyway (ie:- purse, “murse”, favorite backpack, etc). So, while more people peacefully carrying firearms is generally a good thing, one has to be careful about places like airports. My personal method is to never “cross streams” so to speak. Anything I ever use as a carry on is never used for anything firearms related, so that way there no chance of forgetting that there may be something unwanted in there.
This happened a good bit in other countries with military contractors, for things that are far more restrictive, like a single round, shell casing, or a magazine. I’m some places, that’ll land you in jail immediately. Because of that, many individuals chose not to “double duty” their airline luggage / carryon items, just in case.
