No one else from any other country, has said that alcohol consumption is allowed on their public transportation. I think UK is an anomaly on this.
I think it springs from the day when most people were proles working in factories and mines, and their lives were so horrible that they couldn't wait the length of a tube ride before beginning their nightly drinking, especially with the bizarre restrictive pub drinking hours that you had until recently.
Explain that one, you were able to drink on the subway, but not in a pub during the afternoon?