Sustainable beverage cups

[beanald]

Can anyone enlighten me on which cups can be used for which beverages? On Saturday, I tried to use a cup I received earlier in the day when purchasing kombucha and the liquor vendor would not fill it with a beer. She said she could not serve the beer in a "vendor cup." I had to either buy a different plastic cup with a Planet Bluegrass logo or the more expensive metal cup with a Planet Bluegrass logo. She couldn't explain why other than these were the rules and she's just a volunteer. Is this true? If so, is it a liquor law or only PB marketing? Sustainability didn't seem to be a consideration in my case.