Like you, I live somewhere where to some extent, different sorts of people are clustered together, and I'm thinking of two shopping areas with a lot of South Asians.
I found myself wondering whether the traditions and/or controversies around face veils are relevant at all? Those from religious groups where the women don't wear veils not wanting to be associated with those that do, and men not wanting to be associated with women's attire? It wouldn't have to be a high proportion of the relevant population to have an impact, given the research suggesting that a significant factor in whether people do or don't wear a mask is what's the perceived norm where they are.
As I type that, I think there's quite a strong contrast between behaviour in the two areas, both as regards crowding and as regards mask-wearing. I wonder whether there are any factors such as influential religious leaders and/or community leaders? I know that in one of the areas, some of the local doctors and leaders have been very active over the years in promoting good health.
I'm now curious as to the factors like religions, religious denominations, predominant regional backgrounds etc.
But then I note that there are also differences between different high streets depending in part on things like social class etc.