the problem with selling people on face masks is that they're not a binary solution that fully prevents (or fails to prevent) infections

it's more about improving odds

if you stop even half of a hypothetical virus load in your cough or your speech and someone's still in range, their immune system has better odds - fewer viruses to fight off

and from there, the more, the better

because even the legit masks aren't 100% effective
but the fewer viruses get out of someone (and into you), the better

explaining this to people who think anything below 100% effectiveness is basically 0% effectiveness is difficult