As an outsider I suspect I'm missing many of the subtleties, but it does seem to me that here there's the same split between those who play the tunes and those who sing the words. Those who like words, whether to sing along with or just to listen to, don't have the same appreciation of "tunes" as someone who just wants to go diddley-diddley all night. OOPs, was that a bias showing?

So there is a compatibility between a singer-songwriter and a singer of traditional songs, ballads or not, that can generate something of an antipathy to a "tune" that goes on and on with repetitive rythms until eventually stopping at some apparently totally random point.

I don't think this is a difference between singers and musicians, as such - few songs survive well without their music. Perhaps its a difference between music and "tunes"?

But whichever you go for, they're all folkies in the UK. Two nations divided by a common language again? Maybe our ghetto is just too small to form significant sub-groups, but the borderline modern singer-songwriters and their fans tend to be loud in distancing themselves from mere folk music.