If you live in an area where you are literally living, traveling, walking shoulder to shoulder among millions I can see a masks usefullness. The chance of having someone within touching distance coughing or sneezing or physically touching/brushing against you are very good.
I live in a rural area with the largest town of 40k within driving distance and have always followed just keeping away from other folks personal space. I don't see the need for a mask and couldn't wear one more than 60 seconds if I had to. Since all the kids were grown and gone I haven't gotten a bad virus in years. Just showing that shoving 30-40 runny nosed urchins into close proximity to pass a virus around and bring it home is a prime vector even in sparsely populated areas. For those stuck in high population areas with mass transit or forced or have a habit of living shoved up against each other, they need every tool they can get to not pass crud around.
I’ve been through many Asian large cities over the last several years. “Some” people wear masks...not all as some people are implying. Over the several months we collectively spent in these cities we never wore a mask. We’re still here.