To tell you the truth, a lot of the music we like is very different from other types of music, to the point of being something of an aquired taste. Also a lot of the language and story in those songs aren't easily understandable, nor are a lot of the metaphors or images. It takes a lot of imagination and often a fair bit of knowlege of history to give one access to the full power of this music. Also helpful is a inate interest in understanding alternative cultures and ways of life. Unfortunately this doesn't describe a lot of people. For these, the music lacks a context, so that a phrase like 'I'd rather drink muddy water, sleep in a hollow log' may be understood, but won't resonate with their experience. Unconciously their brains go, 'What a strange way of putting it, why put it that way?'.

Who's left? People like us who either a) just find this music delicious at first bite (like the people who fall in love with Gorgonzola Cheese the first time they taste it), b) have the requisite interest in history and culture, or c) who were raised on it as children and learned to love it. Unfortunately thats not a lot of folks.

On the other hand says Tevye, Hound Dog sold a zillion records for Elvis with lyrics like 'You aint never caught a rabbit and you aint no freind of mine'. Go figure.

Maybe what happened is analagous to the Neo-classical revival. They dig up Pompeii and Herculaneum and all of a sudden every new building is like a roman villa. The old was rediscovered, revived for a while, then absorbed into the larger culture which then moved on to other styles.

A rediscovery of the old songs spawned a wealth of interest for a breif time. The culture absorbed the elements of the music that it wanted and moved on. The interest hasn't died out, people just get that interest satisfied by seeking out those elements in thier incorporated form, e.g. in the music of Eric Clapton.

Its like rice or mollasses. Rice grows as brown rice, much more nutritious than the processed white rice, but what do people prefer? Mollasses and honey have more interesting complex flavors than white sugar, but people buy the processed white stuff much more.