Although FolkieDave raises an interesting point I think there is a bit more to it than that. Certainly the virtuosic instrumentalists are think on the ground in the 25 to 35 age group, But a careful examination of the same group will reveal singers in equal numbers.
For a short example try, Jon Boden, Fay Hield, Gavin Davenport, Jess Arrowsmith, Bryony Griffith, Matt Quinn, Cuthbert Noble, Jackie Oates, Damien Barber, Rachel Unthank, Dogan Mehmet etc, etc etc. Trouble is, unlike my generation, many of these are also outstanding instrumentalists too.
Bryony Griffith once suggested (at Chippenham FF) that most of her generation got into folk music/song via morris dancing. Is this a common 'lead-in' for others of the older generation?