I rely on that one band to help the draw of the other bands. I book bands that don't have an immediate draw if I like them. I'll give them a few shots on an off night. If I can see that they are making an effort to bring people in, I will move them to a better night. If it's a local band booking a month in advance and come the night of the show no one shows up, I will be less ready to book them again.
Bands have to put in an effort.
There is no built-in crowd here at the Met. If you've got a Saturday night show and the band doesn't get the word out, no one will come. We advertise, we do fliers, but most of the draw is on the shoulders of the band. People don't come out for live music as much as they used to. More people are going out to see DJ's.