For many years I've been carefully pointing out to people that advertising for cigarettes doesn't work the way they think it works. The "they wouldn't do it if it didn't work" argument is entirely true. It's just that what you think "works" means in this context isn't the same as what us marketers mean by "works".
The truth is that there's almost no relationship between the amount of advertising and marketing spend on cigarettes and the quantity sold. The advertising is targeted at the smoker not the non-smoker and aims to get that smoker to prefer one brand over another. This preference allows for the marketer to get a bigger margin because the consumer's choice set is limited by that advertising. Incidentally the same goes for soap powder, dog food and lemonade.
By way of proving this, here's US ad spend on cigarettes set against cigarette sales:
These facts suggest to me that introducing plain packaging for cigarettes will be just as pointless, just as ineffective. Inconvenience, annoyance and the further ostracising of the smoker will result but it won't make a jot of difference to either take up or consumption of cigarettes.