Because with nicotine addiction, the lack of a timely dose of the drug leads to unpleasant sensations, anxiety, and anxiety. People with the same disease help each other, because they themselves understand that they can get into a similar situation.
Chips and chocolates are not drugs, the need for them is not strong enough to beg others if they are not.
And yes, there was already such a question, use the search.
This is probably a matter of pleasure. For a smoker, a pack lasts 1-5 days (of course, people and cigarettes are different, so the numbers may be different). And we buy a chocolate bar intending to eat it on the same day and enjoy it. How often do you see people smoking on the street? And those who eat chocolate?
That is, not everyone would be ready to share a chocolate bar, and a cigarette can always be fired from someone else.