Masks are quite effective for short-term risk situations.
The key is short-term, say 15 minutes at a grocery store every two weeks for a few months.
Because the virions of coronavirus are roughly 100 nanometers, 1/1000 the width of a hair and 1/30 the size of surgical mask filtrations (about 3.0 microns or 3,000 nanometers), surgical masks (not to mention cloth ones) do not help.
https://principia-scientific.com/e-mask-ulation-the-lies-they-keep-telling-us/