The ONLY reasons I can think of for how poorly masks have fared in terms of preventing cases are:
Masks don't present any real barrier to virus bearing droplets, so they do nothing to prevent spread via indirect contact
Case numbers are puffed up by massive amounts of false negatives.
Direct contact is being deliberately overlooked and people are picking up the virus on their fingers and touching their masks (yes they are) where the virus can easily get inside the mouth and nose. This would mean most people are simply picking it up at grocery stores, etc.
Thus, were SARS-CoV-2 spread primarily through airborne transmission like measles, experts would expect to have observed considerably more rapid global spread of infection in early 2020 and higher percentages of prior infection measured by serosurveys. Available data indicate that SARS-CoV-2 has spread more like most other common respiratory viruses, primarily through respiratory droplet transmission within a short range (e.g., less than six feet). There is no evidence of efficient spread (i.e., routine, rapid spread) to people far away or who enter a space hours after an infectious person was there.
The ONLY reasons I can think of for how poorly masks have fared in terms of preventing cases are:
https://www.cdc.gov/coronavirus/2019-ncov/more/scientific-brief-sars-cov-2.html
If you believe the CDC that is: