Under normal circumstances I make a loaf of bread every other day for sandwiches, using a bread making machine. So that is 500g of flour, 350ml water, 25g butter, 1 tsp of yeast, 1.5 tsp sugar, 1.25 tsp of salt.
My 'peacetime' rationale is to have fresh bread with no additives in it. There are spin off benefits such as the baking smell.
Over the last decade I have worked in different companies and never met another person with a home baking of bread routine. Sure some people have a bread making machine in the loft or have a mum that does it on occasion but making bread from flour is a rare thing in the UK.
So what is going on with the supply?
Truth is that bread flour is not a fast moving item. If I buy a 1kg bag on a Monday and another on a Friday then there won't have been a lot of restocking in between. I will be buying from the same batch.
Therefore it does not take a lot of panic buyers to take all the stock off the shelves for the few people who regularly buy to find themselves with 'flour anxiety'. If you do use a kilo or two of flour a week then you don't have more than two to three kilos on hand. This will be for variety, e.g. strong white and wholemeal, which can be combined with something else, e.g. spelt or granary, for variety.
In truth flour does not keep indefinitely, it will develop a horrible taste over time or even get weevils. Flour is also heavy, so if you have to carry your shopping by bicycle or on foot then you are not buying sacks of the stuff.
Car drivers with large boots/trunks can behave like a horde of locusts, snapping up vast quantities of items like flour that don't cost them a lot to pay for, store or carry. Meanwhile, people who are buying flour partly due to reasons of making their bread more affordable are less likely to have a car or even large cupboards.