But they don't serve a purpose. My local Tesco none of the staff wear masks. About 2% of customers wear a mask. Those staff are working in close proximity to each other and thousand sof customers every day. I see the same staff week after week, they aren't all falling ill. I don't see how everyone wearing masks would change that?
Increasingly, the purpose seems to be largely political rather than public health. Especially in the US, where it mostly seems to polarise pro- and anti-Trump supporters.
What's happening in America is a combination of things. Trump downplaying the crisis, criticising states that locked down, mass non-compliance with lockdowns, opening up too early, whilst the virus was still very prevalent, total lack of test and trace for far too long. Also demographics, living conditions and poor access to healthcare will be playing a part.
Also massively increased testing, as in Sweden, has caught a large number of less serious cases. (The median age of positive cases found in Florida, for example, has fell from 60-something to 30-something). Unlike in Sweden, some of the southern US states *are* having somewhat of an uptick in serious cases, but that doesn't seem to be especially unexpected as they never had a proper 'first' wave.