This thread is an interesting "filter bubble" experience. Here, a city in central europe, nobody I know wears one anymore, even those who were always extra-careful on the cautious side. Basically nobody in stores wears one nor in public transport. Yeah, on occasion you find 1-2 exceptions that confirm the rule.
Probably, this thread is largely visited by those who still do, and ignored by those who don't.
I’ve noticed this a lot with both lemmy and Reddit. You have to go into any thread thinking about the kind of people that post is going to attract because it often times does not reflect the rest of the world
It's a phrase used in a few different ways, but the main one is that if there's a need to specify an exception, that indicates the existence of a general rule. Wikipedia gives the (good) example of a sign saying "No parking, Saturday 8.30am - 1.30am". The fact that an exception has to be described for when parking is disallowed allows a driver to make the inference that parking is generally allowed.
I think EternalExplorer is saying that the degree to which people with masks stick out on the very rare occasions that you see them, the way they need to be specified as something other than the default, just makes it even more clear that the general case is that masks are now absent from public life in their city.
I see some tourists wear one in Amsterdam. Very rarely a local, of which I always assume they're ill themselves or easily get ill (immunocompromised and what have you).