That is exactly what the owner of our local (Rock) venue in Worcester says, Richard.
Mudlark's comment on a demo being representative of what is actually going to be heard on the night is true as well.
If I wanted to sound the same as I do on CD, I'd have to use a backing track on account of my inability to play five instruments at once while singing- and that would be several steps too far for a trad gig!
Cheers
Dave