Sometimes going out in public is necessary, such as to the doctor, or to get food if there's not someone to help with that. And sometimes it requires passing through other public spaces, such as public transportation. A person can have no illusions about the degree to which masks help, but still depend on them because what else is there?

As the spouse and caregiver of a compromised person, I wear a KN95 anytime I go into a store or other indoor public space, to try to avoid catching and bringing home anything that might land him in the hospital again.