I think it depends which folk revival you mean, and where. The folk revival in Britain of the early 19th century resulted in the collection of a lot of ballads which might otherwise have been lost, but also the selectivity of recording- the collectors only wanted ones they thought were good in their own terms- meant that they were recorded in a standardised sort of way, that perhaps didn't reflect how they were being used at the time.

The later 19th century British revival resulted in a lot of material being recorded, particularly collections of Yorkshire and Geordie songs, with a lot of new songs added (Dalesman's Litany for example). Some of this came via the music halls, and has been subsequently incorporated in what we think of as traditional.

The early 20th century views of Sharp and co refocused attention on specifically songs of the country side, as they had a definite image of the unspoilt agricultural labourer carrying an unpolluted tradition that could be recovered. Unfortunately, they didn't think the UAL's style of singing as suitable for their own circles, and produced arrangements to be sung in a light tenor to a polite piano accompaniment, or for choirs of schoolchildren, with content altered to match. This buttercups-and-daisies period again collected and preserved a lot of stuff, but may have also contributed to its dying as a vernacular tradition, by association with the frankly risible sanitisers.

And so on. Our own revival, apart from the period from the mid 50s to the early 70s, has had to struggle against the image of tradition left by Sharp, and later against the image of "protest song" from the period when it was associated with CND etc. (That's where we got the bearded, arran- sweatered, carrot- juice drinking teacher cliche).

The American, Irish, what have you, revivals will have their own dynamics and baggage.

So my take is, in answer to Dick's original question, that not only have the various revivals been relevant to traditional music, it has to a great extent governed what people mean by traditional music.