Unless you wear masks properly and change them at a maximum of every 2 hrs - whilst having sterilised hands etc, masks do nothing but collect bacteria and other nasties.
Consider the average face mask, sits in the car for a week, spends another week in jeans pocket, gets put on face, gets taken off face by contaminated hand, goes back in pocket, repeat this 50 times. Add the time the mask sits on the floor, licked by the dog etc etc.
A friend of mine who is a microbiologist had one of these masks tested in a lab. To put it bluntly, it was like licking a public bathroom floor.