It comes down to economics. With smoking, the airlines were spending money trying to maintain the cleanliness of the aircraft with Tar and Nicotine coating windows, upholstery and not to mention the instruments up front. With Alcohol, they earn money by selling it and would lose tremendously if they were first to restrict and not followed immediately by other airlines. Yes there is the occasional diversion but these are few and banning alcohol could possibly increase the number of disturbances.