In Asia, where mask-wearing is common (part of the culture, nothing to do with COVID), sick people wear masks. It's very practical, and also a social signal that "I am ill". As a manager of a business in SE Asia, people coming in sick but wearing masks was awesome. The mask-wearing reduced their infectiousness (because the mask stops saliva-borne virus communication) and made it OK to come in to work if you're feeling well enough to work. It's socially acceptable to not shake a mask-wearer's hand or otherwise touch them. It's as much social signal as anything ("I might be infectious, I'm not going to be offended if you treat me as a walking virus bomb").

Part of the problem for the West is that we wear masks when we don't want to get sick. Masks don't really work for this (the rest of the mask-wearer still gets covered in virus). And if we're diagnosed sick, then we stop wearing masks. Again, that's not how the mask thing works, because this is when masks are most useful. Both as a social signal and practical way of reducing infectiousness.

To use masks effectively, we need to stop wearing them when we're scared, and start wearing them when we're infected. But I think the social change to do this will be difficult.