80 is wayyy too high when there are severe e shortages of basic items. We have two children and 20 items would last us a week, which is enough. The problem is that people are hoarding for months of food.
Family of 6 here, and I can't imagine how 20 items (or even 20 types of items) would cover us for a week's shop. Going off the typical checklist we've made for doing our weekly shops, our normal once-a-week shop consists of around 30-40 types of items, and we can easily buy 2, 3 or even 4 of some items to do us (for example, we use four loaves of bread a week in a typical week, as we have four children who take pack lunch as we're not entitled to free school meals). A weekly shop can easily consist of 80-odd items, and even doing the reduced shops we have been since this kicked off I'd reckon we're buying at least 60+ items still, and that's not to hoard or stockpile, but just to buy enough to feed four kids and two adults for a week, plus necessary toiletries etc. Cutting it to the bone, we'd still be 40-odd items.
I think Tesco's 80-item limit is probably around right for now to give room to cover families like ours, or a bit larger. Obviously it's overkill for single shoppers, and perhaps more generous for smaller families, but that's where a degree of personal responsibility comes in.
We had some local onion here suggesting that Morrisons should be locking up all of their trolleys and telling people to use baskets only for their shop. My other half firmly pointed out that for us, that would mean filling something like 10 baskets to do a normal weekly shop and even assuming we cut further back than we already have, we'd still be making 7 trips in and out of the shop to do a single shop. How would that square with trying to limit exposure for ourselves (as long as we remain healthy) or to others (in the event we become asymptomatic carriers)? We'd need to spend at least twice as long shopping as normal, in contact with many more people in the shop and at tills than normal, or we'd need to make multiple trips to the shop a week, going against government guidance. Fine for the onion who lived alone and could do a week's shop with an overloaded basket; not so much for families.