That study is biased because it has no proper control group. Individually you may protect yourself with the mask (if you think it is worth it) but that's not h

That study is biased because it has no proper control group. Individually you may protect yourself with the mask (if you think it is worth it) but that's not how the policy makers should look at things on society's level. If most people will not/won't be able to use masks properly, then its effects will be very low.