It may be my libertarded paranoia, but I think airport security screening in the last decade has been largely about diverting public money into private hands.
Metal detectors are so cheap now that they can be placed in urban public schools, and every airport already has plenty of them. Pass-through x-ray luggage scanners are likewise already nearly ubiquitous. Automated gas chromatographs, microwave passenger scanners, and x-ray backscatter passenger scanners--those things are new, big, and shiny, and no one responsible for budgeting knows how much they should cost.
Meanwhile, Schneier repeatedly and convincingly argues that the measures that we are paying through the nose for them to use are worthless to increase the physical security of the airplanes and their passengers. But the TSA already bought them. It doesn't matter if they work. They have them: they use them.
All that remains now is to justify the budget for the labor force. The ID checker, that's a job. The pat-down guy, that's a job. The guys that stand in front of the tablet app that digitally flips a coin to see if you get your hands swabbed and chromatographed, apparently that's three jobs. The guy who stands at the exit to make sure no wrong-way traffic gets through, that's a job for every exit.
Except they're proposing that the exit guard jobs be replaced with expensive machines now, too. Give it another few years and you'll have DNA sequencers and single-use biological test chips involved somehow. Perhaps after the next airborne pathogen scare, they will be introduced to reassure passengers that no one on their plane has ebolaria or influengue or tubercuningitis or whatever.
Conspiracy hypotheses are easy if you just follow the money.