I think they have this figured out to collect the maximum tax revenue. For one, and this is my speculation based on observation in America, supply is off the charts. I mean you can manufacture alcohol in your house or even prison. Over the last decade or so craft breweries have popped up all over the place. It's fashionable and hey, it keeps the tax revenue coming. They want to collect as much tax revenue as they can without a level that cuts demand and overall revenue and tax revenue.
If we drastically lowered alcohol consumption it would be a huge problem for Governments to raise tax revenue that they are counting on. Its a huge problem with tobacco for governments. The e-cigarette should have all but finished it. They did not count on a stop smoking product to actually work.