That's completely false. People are not surgeons. The goal is not to maintain a sterile environment. The masks people generally use are not even rated for that

That's completely false. People are not surgeons. The goal is not to maintain a sterile environment. The masks people generally use are not even rated for that. The situation is simple. With airborn virus, people will get contaminated when they come into contact with droplets containing virus. Given the typical viral load of people having Covid-19, the issue will mostly be with large droplets. These droplets are stoped by masks. Of course, you are going to emit droplets when you are drinking or eating but far less than than you would have not wearing a mask at all. The point is not to gain protection. It's to limit your chance of contaminating other people if you are asymptomatic.