They work if the sick person is wearing a mask to catch large spittle droplets.

Asymptomatic spreaders are not really a thing - so healthy folks really don't need to wear them.

90% of people admitted to hospitals always wore masks in public, so the paper/cloth masks really aren't working anyway.

So if you are sick, or nearby sick people, or in a high risk group - wear a mask. Otherwise it's looking like a complete waste of time and effort.