Because any pathogens you were exposed to in public are behind held up against your mouth for an extended period of time.
The keep-pathogens-out effect is supposed to be this secondary thing, and I’m not under the impression that it’s even that reliable.
In Asian countries this might be different though.
The keep-pathogens-out effect is supposed to be this secondary thing, and I’m not under the impression that it’s even that reliable.