If you travel a lot and you're a smoker you'd know that the worst part is getting off the flight, crawling through the airport at exit and then not having a lighter because they took it off you at departure[1].
No penalty for being caught with a lighter, so I kept leaving lighters in my bag in different places deliberately to figure out how I could get one through.
Solution turned out to be simple, and I hit it almost accidentally. I removed the metal shield and then dropped the lighter into an inside pocket of my bag that contains pens and loose coins.
Worked 100% of the time thereafter.
The scanners being blacklisting like a virus scanner means they have the same problem, they can only identify known threats. Change the form of the threat and you're through until they update and train their scanners again (both human and machine).
The illusion of safety. I've since quit both smoking and flying frequently.
[1] I gave the TSA the idea of handing out lighters they have confiscated from departing passengers to arriving passengers but they didn't buy into it.