The main point is that face masks are known to not be full proof, and badly worn ones might even be less effective than not wearing anything as they provide incentives for people to repeatedly touch their faces. More importantly facemasks create a false sense of safety and thus invite unwitting people to needlessly expose themselves to the virus.
If you want to understand the problem, think of combat helmets. You can put one on and safely walk into a war zone, right?
The mask is not protecting you. It is protecting others from you.
If you were right, and wearing masks badly would have been worse than not wearing them at all (i.e. w.r.t. touching your face and all that), then countries that opted for mandatory mask wearing would be worse off and they aren't.
Related: https://www.preprints.org/manuscript/202004.0203/v1
You're misrepresenting the entire problem.
The main unknown is not that protective equipment helps protect. That's a absurd strawman.
The main unknown is the impact on the likelihood that someone not educated or trained or experienced in facing biological hazards would contract a virus when knowingly exposing themselves to the virus while wearing said protective equipment to the best of their personal abilities, discipline, and knowledge.
That's the main unknown.
Meanwhile, do keep in mind that the effectiveness of condoms to stop unwanted pregnancies, which are pretty much widespread and even covered by classes included as part of mandatory public education, has been as low as 79% if poorly used.
https://www.webmd.com/sex/birth-control/birth-control-condom...