Susan, I don't know if they have changed much over the last thirty years but, when I played at English and Scottish folk clubs, the audience needed no encouragement to sing along and rather well, I might add. Irish audiences were more rowdy, as a rule, attentive but not allowing the music to interfere with their socializing.
Back in the day, no folk concert lacked a load of singalongs. No one attended a Pete Seeger concert, expecting to just sit in a seat and listen. The same for most other folk performers. That was my school, 1950's folk concerts, and it is why I still perform with a majority of singalongs.
I think that today's dearth of song leaders is because of the desire to express one's self, the need to do so through original writing, the disdain for the familiar.
Outside of that, how you doin', Susan?

                        Mike