Yes, as Tim says, the places where the songs were collected are not necessarily their place of origin. The early collectors had an understandable tendency to go to easily accessible places, which are probably over-represented in their collections.

A number of the songs that are about local or regional events are in fact quite recent compositions. This doesn't make them bad songs or less interesting songs, but it may mean there's nothing particularly distinctive about their regional flavour, except for the events they're describing, and possibly some use of dialect.

I suppose the regional characteristics of music and song are becoming less distinctive anyway, now that so many of us travel out of our native area and move around the country. The folk community also meets up at various festivals and folk days, exchanging tunes and songs, and no doubt learning from each other's playing and singing styles too. A similar levelling-out is happening in our language, as the more extreme forms of dialect are slowly dying out.