Espiner's explanation for increasing the latter but not the former is that they couldn't do them both together, without creating an outcry, and they didn't want to do the tobbacco tax in the budget. But that still doesn't answer why raise one tax and not the other.
I can think of two explanations:
1. Machiavellian politics: National are unlikely to scare their voters away from National to Labour with nanny-state policies, but they might to ACT. Voters at the National-ACT margin are likely to drink alcohol but not to smoke. At the same time, however, the cigarette tax might shift voters from the Maori party to Labour. Given the overhang, such a shift would likely reduce the number of Maori MPs but not increase the number of Labour MPs, a situation that might suit National.
2. Gilbert and Sullivan politics: When you can't find the analogy you are looking for in Shakespeare, WS Gilbert is a good place to look. There is a wonderful chorus of the jury in Trial by Jury in which the jury respond to the defendants explanation for his wayward behaviour:
Oh, I was like that when a lad!
A shocking young scamp of a rover,
I behav'd like a regular cad,
But that sort of thing is all over.
I'm now a respectable chap
And shine with a virtue resplendent;
And therefore I haven't a scrap
Of sympathy with the defendant!
Some of the tut-tutting of our youth drinking culture that has accompanied the Law Commission report seems to have a touch of this hypocricy. Could it be that the reason that that has been a restraint on our politicians? Most of them probably have never smoked, but do have episodes of excess alcohol consumption in their past.