It's all for show to get people accustomed to complying with unreasonable demands. They've ruined travel for me and I do far less of it now. I absolutely hate having to take off my boots and feel like a criminal just to get on a plane. I certainly don't feel like it is for my protection because as you demonstrated it is not a system that actually works.
Last big trip I took was about five years ago, I was at the Frankfurt airport and it came on the news that a child in the UK had managed to catch a flight, making it through every single checkpoint without being detected. He had no boarding pass and was alone. He only got caught because he told someone on the plane while it was in the air.
Watching them scramble to give the impression of "increased security" in response to this was amusing. We all had to line up and have our passports scanned while they questioned us and then we lined up and went through the regular process - it was a completely absurd reaction to the given situation and yet, we all lined up and complied.