Security theatre and the airport

If you stand on any given day in a major airport, look around. You'll see people taking off their shoes and putting them in a plastic bin. You'll see people taking their laptops out of their bags and putting them in another bin. You'll see people removing liquids from their luggage and putting them in a transparent plastic bag of no more than a litre. You'll see people standing with their hands up in a body scanner producing a vague grey image of their body. You'll see a staff member swabbing a handbag with a cotton swab and putting that swab into a machine that gives a green or red result.