The authors of this article in Scientific American take great pains to allege there is no evidence they don't work, but are also forced to admit there is no evidence they do. Not only that, we had 10 RCTs performed since WW II showing no evidence of working to contain flu spread - another fact you ignore.
Link: https://www.scientificamerican.com/article/what-went-wrong-with-a-highly-publicized-covid-mask-analysis/