The point of the masks isn't that they're 100% effective, but that they reduce the probability of spreading a virus-laden droplet to someone else. The difference between having a pandemic and not having a pandemic is the question of whether the average infected person infects more than one other person or less than one. N95s or basic cloth masks are a relatively straightforward way to get a population on the other side of that threshold, even if some people wear them incorrectly were just unlucky.

If there are better masks than N95s for dealing with carcinogens like asbestos, you should use those for that application. Maybe they would work better for Covid too, but providing super high-quality fancy masks to hundreds of millions of people in a pandemic isn't really practical, though. You use the tools you have on hand. Even distributing N95s was challenging.