What you wrote isn't entirely accurate. As stated by Professor Hajek and Robert West (in the comment below yours) the problem is anti-tobacco advocates have managed to convince smokers that e-cigs are no less harmful than smoking and that's why there's a decline in smokers switching at all, rather than it not being to a first generation e-cig. I think Dr. Farsalinos stated the decline is as much as 30% in three years, if I remember correctly. Either way, there are links at the bottom of this article to a couple more articles about how relevant evidence gets misreported for political ends that would explain how big the decline has been.

When even vapers agree to vaping bans where-ever smoking is banned you know anti-tobacco advocates are winning.