They may call in a mediocre band, since it's in their budget. The mediocre band may draw the best because since they don't play out that much, they can get friends and family to watch them for novelty. The dive bar owner loves it, because they have a good night without paying the band and rebooks that band. Unfortunately, they don't repeat their draw, because even friends and family don't want to see a mediocre band all the time. The bar owner is mad because they didn't draw, and scared off the regulars, so the mediocre band gets their shows cancelled. But, since they had success with a mediocre band before they try again, and again until the place's reputation is worse than before.
So the bar owner determines that having bands is losing proposition, and buys a photo hunt machine for the regulars to play with so they can make an extra $10 a night.
The problem is that even a great band will have a hard time overcoming the difficulties of a dive bar: poor promotion, bad service, bad food, watered down drinks, bad location, lousy atmosphere, etc.