The airports will never go for banning duty free or any sales to passengers. Go it to most UK airports and you'll see large podiums of miniature spirit bottles and small bottles of wine right on the walkway that every departing passenger is forced to pass by. They're blatantly designed for passengers to take onboard and drink. When challenged by my airline due to alcohol fuelled disruptive pass the airport said 'these are for people who may want a drink on their arrival in their hotel'. This may be true, but isn't that why they invented mini bars? The airport is interested in selling and making money and nothing more.