“more will make a mistake”
When you pack your bag, do you just “make a mistake” and put your gun in there?
When I fly, I make a pretty conscious decision not top put guns, hash oil vapes (that Grindr dude), hunting knives, etc. in my bag. It would be more than a mistake, if they fell in.
Everyone makes mistakes.
1 person out of 100,000 flyers making a mistake is a very small fraction.
The psychological reasons can be very simple. Someone in the household places the gun in a carry-on, because they believe that is where it is supposed to be.
It is down in bottom, perhaps covered by other material. The person who uses the carry-on, checks quickly, but does not see it, or they are in the process of checking when they are distracted by an emergency, such as a child coming to them with a cut finger. Their mind says they checked, but they did not.
It is amazing how Murphy can trip people up.
No one is perfect, except for people on the Internet.