There's also a competition element in bigger cities and towns - what are any competing attractions tonight? In smaller more rural venues there's a better chance sometimes of atracting an audience if it's about the only thing that's happened locally in living memory ------ or the last couple of weeks!
Certain events that my friends and I have put on have been bedevilled by some other great attraction on the same night, which we only became aware of a few weeks before ours - which had been planned months ahead. No matter how well you research this, you will inevitably get caught out on occasion through no fault of your own.