"It is important to wear a mask or respirator when you are sick or caring for someone who is sick with COVID-19."
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-si...
"Wear a high-quality and well-fitting mask if you must be around others (for example: going to get tested), even in your home."
https://www.health.state.mn.us/diseases/coronavirus/sick.htm...
Framing masking as protecting the wearer was done to psychologically make people care. People are more likely to care about themselves, than others.