It is a nuanced issue though. There are recommendations from the World Health Organisation which say that in a community setting, for a well person “a medical mask is not required, as no evidence is
available on its usefulness to protect non-sick persons“, but that a person with respiratory symptoms should wear a mask [1].
In a medical setting (or very close contact, like a few metres or so) they do help in both directions, this is standard “droplet precautions” one usually takes with a patient.
So while I agree with you that it does help in the medical setting, there is really no evidence that wearing a mask on the street protects yourself, rather than protecting others.
[1]: https://www.who.int/docs/default-source/coronaviruse/advice-...
As a secondary benefit it stops you from touching the critical areas of your face. Given that we touch our face hundreds to thousands of times a day, a few adjustments of a mask aren't going to offset that.
The myth that the mask purely protects others is a myth that needs to die. At this point it is truly destructive.
Given that a surgical mask is only of limited protection, and not total protection, of course in actual contagion situations medication professionals should have something much better. Though we're in a situation right now where the CDC is telling medical professionals to fashion masks out of bandanas.
But when you see the streets of China where everyone is wearing surgical masks, or you see some old person walking around with one, note that it absolutely does reduce their risk. Not anywhere close to completely, but to some degree.