"What is the attraction of doing something outwith of at an event?" -

To many of us, as Leadfingers has said, folk music is something we do, rather than what we just listen to - "Music in the Community".
Formal concerts provide a nucleus, and usually we do dip in and out, but several days of just listening to other people - no matter how skilled - doing it gets boring.
You might even consider that the point of a folk concert, from a musicians point of view, is to see what the "leaders in the field" are doing, and take it away with you as inspiration for your own playing.