If you want to attract newcomers and/or audience you would have to advertise, and then who knows what types you might get turning up, also licensing problems.
If you don't, then it all gets a bit mutually masturbatory, if you know what I mean.
I guess much is a bit like that (MM) anyway. I for one don't play to an audience. As far as it goes is I like to think there might be a couple in the room who enjoy the music and that listening or otherwise a landlord feels he has enough custom with our presence (in some cases more a matter of not driving existing custom out than attracting extra trade...),
The hope of finding new to the music musicians and visiting musicians, I think would be a concern though. They seem so hard to find even in public places...
Overall though, I think between this thread and an artist centre thread, I think there is a widening and perhaps at some point permanent spit between the "professional" schools of thought and the "amateur" (which incidentally need not included "its only folk so...") schools of thoughts.