true, they stop YOU (the person wearing the mask) from transmitting what YOU have to others. But they do NOTHING to stop YOU from getting the Virus from others.
They do nothing? Or do they reduce the odds of transmission to some non-zero amount? I wear gloves when changing my mower blade not because they guarantee I won't slice a finger off but because they make injury much less likely.
[true, they stop YOU (the person wearing the mask) from transmitting what YOU have to others. But they do NOTHING to stop YOU from getting the Virus from others.]
Then why do healthy nurses, doctors, and other personnel need them?
Do you think that the nurses and doctors in a corona virus ward wear masks to protect the corona virus patient from getting the virus? No, they wear them to protect themselves from contracting the disease. So, it is logical to assume that they do provide some protection to the wearer, IMO.