The mantra about the mask is "It doesn't protect you from other people, it protects them from you!" Mask wearing is supposed to be altruistic rather than preventative.
People take this to mean they don't need to wear a mask if they don't feel sick. Yet you can have C19 and not know it for days, or you might never know it. So, people won't be wearing masks when they need them because they don't know they need them.
So, the mantra should be: masks stop transmission.
Don't make mask wearing conditional on the health of the wearer. Don't make it altruistic. Just require it.