Because they don't want to infect others. In normal practice masks are worn when sterile or high risk surfaces are exposed and no risk can/needs to be taken. Wh

Because they don't want to infect others. In normal practice masks are worn when sterile or high risk surfaces are exposed and no risk can/needs to be taken. Which is about all medical professionals use masks for. If they know somebody is infected they use physical shields, because that is the only thing that will prevent exposure. A mask used as a shield isn't used in a professional setting because what it is is guessing. It can't hurt so sure wear it if it makes you feel better, but all you are doing is guessing, not preventing.And if you want to tell others they must wear them you are saying they have a high probability of being infected. Which you don't know, just are afraid of. Don't tell people what to do based on your fear, that rarely goes well.