I think they're also helpful in filtering out some of the air pollution when it's up.

Just for grins. I put on a mask when vacuuming and dusting. And noticed a significant decrease in coughing and sneezing afterwards.

I also wear a mask in surgery to prevent bacterial contamination to patients. And when entering any hospital isolation room.

But no, you don't need one all the time. It's just a matter of personal choice. Except in surgery, hospital isolation rooms and clean rooms etc..😊