You keep saying this as if it were true, but it's not.
There are mechanistic studies in controlled laboratories that do not take into account behavioral science and the fact that we don't live in a controlled environment. Most of these studies are observational in nature, which sit near the bottom of the evidence pyramid in terms of quality of evidence.
So let's look at what the CDC has to say about face masks in their own systematic review of 10 RCTs spanning 72 years (emphasis added). Since you're such a science-y guy, I'm sure you know that systematic reviews of RCTs sit atop the pyramid in quality of evidence;
One study evaluated the use of masks among pilgrims from Australia during the Hajj pilgrimage and reported no major difference in the risk for laboratory-confirmed influenza virus infection in the control or mask group
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Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza.
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The overall reduction in ILI or laboratory-confirmed influenza cases in the face mask group was not significant in either studies
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None of the household studies reported a significant reduction in secondary laboratory-confirmed influenza virus infections in the face mask group
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There is limited evidence for their effectiveness in preventing influenza virus transmission either when worn by the infected person for source control or when worn by uninfected persons to reduce exposure. Our systematic review found no significant effect of face masks on transmission of laboratory-confirmed influenza.
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Proper use of face masks is essential because improper use might increase the risk for transmission
Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures
Interestingly enough, this is exactly what we were told at the beginning of the pandemic... until it became politically convenient to shift the blame to people for not masking.