Wearing a mask can help keep any dropletts from reaching others if you happen to have the virus and don't know it.
The mask also helps keep you from breathing in any contaminents.
Even though they may only be 86% effective, something is better than nothing.
Wear a mask shows you care about your own health and that of others.
Not wearing a mask indicates you don't give a d*mn about your health or that of others.