..which leaves out the Global Pandemic part.
I told you folks about face masks back when this all started, when you saw pictures of people in Asia wearing face masks- they were the ones who were contagious.
The mask doesn't make you a social outcast, it just tells the rest of the crowd that you have the crud and you don't want to spread it around.
Don't over-think this idea. Its mostly a nice form of social etiquette when you live in a high density population.