Nobody claimed they were 100% effective, just that they are very useful, especially N95s. Can you not get that? Steve Alford didn't make 100% of his free throws, but having him at the line was a useful scenario and way better than having Shaq at the line.
Masks certainly work a lot less well when the ones NOT wearing them are spewing virus everywhere, like your hero was before the debate.
scenarios (now think carefully)
1) A sick person wears a mask and meets a not-sick person wearing a mask: pretty good. Sure, it would be far better if the sick person wasn't around anybody, as much as possible, even while wearing a mask.
2) a sick person wears a mask and meets a not-sick person
not wearing a mask: not as good. If that sick person's virus gets out (it's not a magic bubble), then there's trouble, since the not-sick person is unprotected.
3) a sick person
doesn't wear a mask and meets a not-sick person who
is wearing a mask: also not as good. That sick person's virus is spewing everywhere, so the not-100% effective mask is going to be challenged. But better to have Alford at the line, not Shaq. But if you make him shoot 20 FTs, Alfrod might miss and one miss is all it takes.
4) a sick person
doesn't wear a mask and meets a not-sick person
also not wearing a mask: the worse case scenario. That sick person's virus is spewing everywhere, with nothing to stop it. Shaq on the line, blindfolded.
That's how Trump knowingly infected 10 of 11 people that he was with in debate prep.
Could you read all of that? I hate to go all cosmic on you, but this is important, and it's BASIC STUFF.