Even in their heyday, folk was a minority interest and folk clubs were places for people who were interested to go to listen to folk music. I don't recall any feeling at the clubs I went to that we should go out and proselytise to the other people in the pub - they just weren't interested. If you were interested in folk it was usually fairly easy to find at least one club through newspaper advertising, and from there to find others as they all shared information.

It's the same with sessions - they're primarily intended to entertain the musicians and others who go for the music. If other people enjoy it too that's fine, but the session will take place whether or not there's an audience.

What I regret is the comparatively few opportunities there are now to listen regularly to good professional performers, supported by (usually) competent amateurs. Now it seems to be a choice between occasional and expensive concerts and singarounds or sessions. Of course such clubs still exist, but they're much fewer on the ground - time was every town would have one.