Isn't it generally true that people go to work for the government so they do not have to think? They just follow a manual, no concern as to whether it makes any sense or not?
Everyone seems to have a story about how they accidentally smuggle something in.
Mine is this - I have a big rolling laptop bag. I flew from Sacramento to Burbank in the morning. Just the normal useless laptop in its own bin.
In the evening, going through security in Burbank for the return trip, TSA says "we'll have to inspect this bag." Then he undoes a couple of zippers and reaches down in it, and presto there is my leatherman I lost about a year ago! "You plan on flying with this?" "Well, no, I didn't plan to, but I did this morning!" Actually they were super nice about it, and my travel companion checked her bag, with my leatherman, so I didn't have to throw it away.
Good thing I didn't know it was in there eh? First I would have dispatched all the passengers. Then I unscrew the hinges on the cockpit door (with the handy screwdriver part). Or I just saw the dang door right off with the 3" saw. HA HA! It is I, the Leatherman Terrorist! Prepare to be multi-tooled to death! I use the pliers to disengage the autopilot....
Friend of mine went through security in LAX. He was going hunting in Mexico. Sat down in the plastic chairs, reached into his bag for his book, and there's a pistol clip full of 9mm bullets. Just about shat hisself. He didn't want the airport shut down, so he put it in a paper food bag, and dumped it in a garbage can.
If all these WMD's are getting through accidentally, what could happen with people that are trying?