Think of the mask the way you think of your baby nappies. We don’t wait for babies to poop all over and then we clean as they move along or start spraying the room. That is what some governments are doing. Masks are easy to make, and Drs in the US are resorting to home made masks (due to shortage). Masks ensure less secretion of droplets into the air/environment for those infected . And did you know if worn all the time they also ensure “nose pickers” and persons who keep touching their mouths get frustrated!