How do people know they can drive properly? How do people know they have good control over a weapon? How do people know they can do their job well?
People need to take good care of their bodies, eat well, and get exercise. Those who know they're sick should wear a mask to prevent spreading it.
And if a mask can prevent the virus from going out, it can prevent the virus from coming in. People who are scared can wear a mask.
In the USA, medical malpractice kills as many people YEARLY as the coronavirus has killed this year. Before people demand masks to cull a virus, we need to worry more about the medical system.
Also, completely preventing death is impossible. Many people who have died from the coronavirus had poor health and likely could have died this year of another cause. I don't mean to downplay their deaths, but putting a mask on everyone and staying in lockdown is a bad idea. It needs to end eventually.