I don't doubt your perspective on the issue, I'm just saying that it doesn't represent the wider response, which has very much shown that plain packaging has had a moderate impact. See, for example,
http://www.tobaccopreventioncessation.com/Re-analysing-tobacco-industry-funded-research-on-the-effect-of-plain-packaging-on,78508,0,2.html
and other studies are similar. That's not to pretend that on its own plain packaging is enough, but then again that isn't the argument anyway. It's part of a wider strategy.
The same would essentially be true when it comes to cereal packaging. On its own I don't dispute that it will have only a minimal impact (although crucially not no impact at all), but if there are wider efforts to, say, reduce sugar content of all cereals, and the like, then it would play a significant role.