in my experience some folk clubs do pull from the local community,here are some examples
Swindon folk club most of the people attending live in the Swindon area,Wilsons folk club,most people from the nearby area,Stockton folk club like wise,Darlington folk club like wise,and quite a few others similiar.
I can also name clubs such as Robin Hoods Bay,where local people attend,but also have alarge proportion of holiday makers.holiday type destinationsare always going to have plenty of outsiders.
I agree with Ralph that big cities are a different scenario.
as Bryan says much depends upon the organiser