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The reason why non-essential shopping is cordoned off is that it is exactly the place that attracts those who do not use face masks properly and do not sanitise their trolley handles! Seriously though, it is to limit the exposure to virus by limiting the amount of time a shopper spends in the shop. But it is not either or as you seem to imply, it is all three.
As to air hand dryers, I fully agree with you, what an efficient way to circulate droplets and even aerosols! Nobody seems to have cottoned on to this. They should be banned, but of course one aspiring ventilator manufacturer who makes masses of these SARS cov2 spreading machines, might object on the basis of free trade and discrimination against the spread and thereby reduction of profits both ways, lesser spread lesser use of said theoretical ventilators, lesser profit all round.
The deployment of the army to deal with public health matters is appalling. Why not use tried and tested public health routes and build them up instead of privatising to inefficient dido-friends-of-the-tory-profit-making-catastrophe-fund? But of course we know the answer.