Put a guaranteed tax stream (i.e., take off of the cover charge, which everyone entering has to pay) vs. a potential tax stream (i.e., booze, which not everyone purchases in volumes) and any tax agent worth their salt will choose the guaranteed tax stream EVERY time.
Furthermore, you actually think the state government tax officials consulted bar owners before pulling this one? I highly doubt this.
Like someone mentioned, though, smart bar owners will switch it to "skirt night" or "strapless dress" night, just to keep doing what they always have been...