The thing with masks is that they are not designed to protect the wearer. A doctor wears a mask to protect the vulnerable patient from infection. If the patient is known to be highly infectious then they wear a lot more, like full covering.
Asians quite often wear masks to not infect others. It is part of their culture, so it is not uncommon to see them all wearing them all the time, especially now.
The mask actually is a collector of germs so it needs to be thrown out or washed each time. Touching the mask to remove it exposes you and you should wash your hands immediately.
In Australia we are being told not to wear masks as they need them for medical people. A few are complaining but all of the experts are saying not to wear them.