Why japanese people wear masks

The masks are in case you are sick and you don't want to pass it to others.
The mask helps a lot !
Others use masks because there is polen in the air and they have alergies.
Or to cover pimples.
To not swallow the car's smoke , or just for the sake of wearing a fashionable mask.

Maks should be international , so other people don't get YOU sick !!!!