Aren't you two eager to jump to conclusions. By drop out of fashion I mean the number of people smoking decrease to almost none as a consequence of social pressure, not that all people smoking are doing so to look cool. I'm well aware that smoking is enjoyable.
Smoking is being portrayed as antisocial behaviour by removing smokers from social situations and emphasising/exaggerating the harm smoking does to other people. Emphasis is also placed on it being expensive and offering no perceptable benefits, often glossing over that smoking is a pleasant experience. If smoking is considered stupid by the non-smoking majority as a consequence of this, then smokers are therefore stupid, and people do not like to appear stupid.
Fingers crossed you two will actually read this and not just come back with "what gives you the right to call me stupid".