You're right that they'll take it into account, but there are other steps they'll take before shutting: more stuff going behind the counter, etc.
I think the logical conclusion, if things get steadily more dystopian, are supermarkets that look like a giant off-licence: all staff and product behind barriers.

Generally, deliveries are OK (I think this just depends on the quality of the local workers) but there seem to be more problems further up the chain in the offices or depots. For example, I sent off the form to replace old stamps with the QR coded versions several months ago, and never heard anything back, so that's a fiver down the drain. My small act of protest will be to refuse to buy any postage from now on, and try to use alternatives if I absolutely need to send anything physical.

edit: I actually contacted RM about it: they said the stamps were sent out, and agreed to send another lot, so that worked out OK.