"duty free"...
Most of the destinations that cause us the most trouble, IBZ, PMI, ALC are within the EU, and so it is not duty free. In many cases it is more expensive than in your local shop. It is the mindset that says you need to buy a bottle of vodka for a 2 1/2 hour flight...
And out of 200+ pax, only a few will be a problem - why should the other 95% be denied a drink to start the holiday they may have been saving all year for?
Stronger penalties, the sale of only true duty-free, and the banning of airport shops selling miniatures - why would they do that? The airports and airport shops hold more responsibility here than the airlines...