The concept of citizens wearing masks to keep things from going IN evolved in China, because in some places the air is so polluted, there are large particulates in the air. So the mask helps somewhat in that situation. Except those people people only live to about 50 after a lifetime of breathing poisoned air. The air is so dirty they have a mask ring around their face after riding a bike.

They wore them in New York City as well for years now, the bike delivery guys, again, to keep things from flying IN while they are on the bike.

Some food preppers already used to wear them for the main reason any professional does, to keep whats in you from going out.

Even in a surgical situation you can't stop small particulates. The mask is to guard against unexpected sneezing or coughing.

BTW the claims that N95 or other masks keep out microparticles is total BS. By the time you start sweating the seal is broken, so keep trying.