From what I understand the masks are utterly useless against this anyway.
Source: https://www.cdc.gov/coronavirus/2019-ncov/hcp/respirator-use...
Yes, but given the incubation period and so on, how do you know you don't have the virus?
I'm not going to wear a mask in Central Europe (at least not yet) but I probably would in Asia just in order to not be selfish.
They aren't perfect because you still need proper technique when removing them and they "leak" along the sides etc. Still better than nothing, especially in crowded places.
They may help you to minimize the spread if you are already sick, sneezing and coughing. Droplets are big enough to be stopped by mask. This is actually the reason why surgeons are wearing masks in the first place - not to contaminate the patient.
Unless we are talking about something more advanced. Like above mentioned N95.
The key insight, though, is that water droplets carry viruses; viruses can travel through masks, but they can't travel by themselves without hitching a ride on a water droplet.
This is why flu season is during the cold winter, when there isn't enough heat to instantly evaporate the moisture in the air. And this is why even a regular surgical mask can offer some protection for a healthy wearer.
I have asthma, and even a few hours of wearing a procedural mask, let alone an N95 mask are very taxing. Maybe for brief periods in public... But sweat transmitted by hand onto a surface is enough. Sewage in a building is enough to infect residents that don't otherwise encounter each other.