I believe that it's to enable a 'vapour check' to be performed. A sealed bag will prevent/reduce the dispersion of chemicals that are being looked for. So providing certain liquids are actually as dangerous as they are purported to be, it may makes sense.
And when have you ever seen such a vapour check being done? Eh? Never.
This is all about profiteering. I had my own resealable plasic bag, but was told it was too large (A4). So I had to pay €1 to by a smaller one (A5).
THAT, is brain-dead profiteering by Numpties. And if you question a Numpty about why they are being numptyish, they threaten to end your career by taking your pass.
Its about time the boot was on the other foot, and some Numpties get terminated.
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