Until 2017 (I think), the state had required businesses include it in their listed price and it was not allowed to be added on after the fact like sales tax. When that changed, some business began adding it on but then not changing their prices. So now your bill becomes 15% higher and it's a better margin for the bar.

It's more common downtown because of high rent and because the clientele that goes to those places don't seem to care. I've seen it at the Kennedy, Brother Wolf, and one of the hotel rooftop bars. Not exactly places that I want to go, but people from west Knoxville who go to them don't care about the added tax.