PR exercise?

Of course, it could be pointed out that for all the money and time spent on elaborate scanning equipment, as far as I know, they have yet to be instrumental in foiling a terrorist plot.
Luggage to be x-rayed
All just for show? A reassurance to travellers and a deterrent to terrorists

Indeed, many people will say that scanning at airports is nothing but a PR exercise - there to reassure the overwhelming majority of law-abiding passengers while also acting as a deterrent for violent fanatics.