It can also be a culturally-adopted thing. From the 90's til now, wearing a mask was normalized to be necessary while navigating through cities like Taipei with dense smog and particulate matter. There's a reason why it's some times referred to as the moped capital of the world.

I guess when word got out that there was a potential spread of infection, Asians had no problem adapting mask wearing on other forms of mass transportation as well.