In fairness, I think it's also very hard to remember to bring a mask around with you everywhere, so you would hope a portion of those people you see aren't being wilfully ignorant of the situation. I was finding that while I wanted to wear a mask all the time, I would only remember when going to do the weekly shop in Tesco, never when I was just nipping in to a shop to grab something.
I've since got one of those thin cloth masks that fits in my wallet when folded, so I don't have rely on my decrepit brain to remember to bring one. Shopping centres should have cheap, single use masks for sale, so that shop owners can say "I can't let you in, but you can buy a mask from over there and come back".