by that token; you can argue HIV is endemic and nothing should be done about it... people will understand wearing condoms but apparently can't understand masking... hmm... neither are very difficult to do, I'd argue that wearing a condom is more tricky in some aspects.

the reason is simple: wearing a mask reminds people there is a risk and it doesn't "look good", despite its many advantages for many pathogens and pollutants; also acknowledging indoor air quality is crap is hard for businesses (and governments) to do since they would need to invest into better ventilation and filtration systems.