They wear those surgical masks to protect themselves from cedar and cypress pollen.
In the last 25 years or so, more and more people started having allergic reactions to the pollen.
And they take antihistamine, (it makes you sleepy!) and wear surgical masks, (they are not the sexiest items to wear!).
As for me, I was perfectly okay with the pollen until 6 or 7 years ago.
So it took me many weeks to realize the constant sneezing and runny nose was the symptoms of "pollen allergy.
It is said that the cedar and cypress trees in the forests in Japan have been neglected for too many years. And they are releasing pollen every spring like crazy.
The reason for having neglected the forests is simple. It was cheaper to import wood from other countries...
I believe this is an important message from the forests. The nature always send us messages and signs, but not in the human languages. We need to find those messages and signs more carefully and humbly.
Instead of fighting with the nature, I try to get alone with it. What worked for me was drinking "cedar tree essence."
It tasted like very weak green tea.
After taking one bottle of the essence, all the unpleasant symptoms magically disappeared.