I don’t understand it either, Steve. I went to the farmers market this morning. Lots of vendors with great stuff and lots of customers - 100% wearing masks even in the heat. Went to Walmart and 100% wearing masks. All good.
Local Casey’s very few wearing.
I fully understand a cheap mask isn’t going to protect me much. But is it so terribly painful to put one on for a few minutes in an air conditioned store. Maybe, just maybe, you are positive and asymtomatic  sp. Maybe it could save putting some elderly person at risk.
I believe the old-fashioned term is called courtesy.