Presumably it's to avoid suspicion and liability. Re-selling is strictly forbidden by the rules here, and losing your liquor license is the worst possible thing

Presumably it's to avoid suspicion and liability. Re-selling is strictly forbidden by the rules here, and losing your liquor license is the worst possible thing to happen to a club. To put it in perspective: If there's a report of using drugs in the bathrooms nothing will happen, it takes too much police work to amount to anything, but a single incident of alcohol leaving the premises can get you shut down. They're super strict about this.