I fear I lack the wit to convey my meaning. None of the aforementioned are folk singers, with the possible exception of Roger McGuinn these days, but all were influenced by folk music and perhaps in turn influenced others to seek out the origins of some tune or lyric which caught their fancy. I expect that's where I got the idea (doubtfully original) that folk music can be successfully purveyed unto future generations in many ways, of which this is one. I think it definitely qualifies as a method of 'attracting new blood' in the sense of the OP. I don't suggest this is in any way a primary propagator, but should be in the mix somewhere. Many other ideas are suggested in above threads.

In some ways, many folk tunes could be blasts from the past, just not electric. Would James Hogg's mother be Robert Hogg's wife? Google is such fun ;)