It's not anywhere near everyone.
I've just been into our high street, and by and large people were keeping well away from each other, I went into Wilko (surprised they were open - hardly "essential"), and again people were being sensible, then to Waitrose, I expected it to be busy, but there weren't that many in, certainly no queue to get in, and again everyone being sensible, didn't see anyone in a shop without a mask (apart from kids), walked about 2 miles in total, and didn't see anybody acting irresponsibly or selfishly.