Yes they are. The government proposed removing them from the CPI arguing that every time they put punitive taxes on cigarettes it had a disproportionate effect on inflation figures. The unions objected, ostensibly because a lot of their members smoke, others believe their real reasoning was that the government wanted to massage the inflation figure downwards so they could offer lower pay increases. Of course these reasons are not mutually exclusive; it is a matter of opinion which one predominates in union thinking.
Interesting topic.
I see your arguments and they do have merit. Taxes on cigarettes do hit the poor more, as it is one of their few pleasures in life.
However as the poor use the public health system more it does sort of equal out when they get sick from smoking! As they paid all the taxes on the cigarettes in the first place!