I see that as the main problem mate. Whatever anyone thinks about corona there is good scientific evidence that in enclosed spaces masks can reduce transmission of respiratory viruses and possibly reduce the viral load if you are infected but only if everyone is wearing one in said enclosed space.
I wouldn't force anyone to do anything but I do think a couple of the main supermarkets should come out and say they are putting on security who won't let anyone in without a mask. Then people who want to wear them and want those around them to wear them can go there and word will get around where it isn't enforced and everyone is happy.
Would be a good experiment as well seeing how that worked out