How much profit does a major airline, i.e. United, AA or DAL make from one year of onboard liquor/beer $ale$? How about KLM, BA, Air France, Lufthansa...? Are these revenue/profit figures more classified than the previously 'confidential info' in a Tom Clancy novel ("Hunt for the Red October"...) or gadgets on the US Navy EP-3?
This is the main problem and the US FAA is merely a collaborator-they don't want to figure out how to partially or reliably enforce the FAR which refers to intoxicated passengers being verboten, not that there is a simple solution without gate agents finding time for breathalyzers with a large airport policeman watching each result in case of an arguement.