That depends on your definition of quit. If you mean stopping the use of cigarettes, and vaping entirely, yeah I can believe the success rates are that low. But....why should we not celebrate quitting cigarettes, even if the majority of us continue to vape the rest of our lives? I'd say ecigs are a pretty good means to significantly lower your risk of smoke related illnesses. And then there are the Zero nic users, which kind of defy the concept of either category. Did they "quit" even though they're still vaping? Are they still considered "users" even though they use no nicotine?
Like I said, it depends on your definition. I suspect the skeptics (and those who seem to have such a problem with vaping....idk why) do their very best to make the scenario sound as bad as possible. Even if, by your personal definition, the quit rate is only 30%, compare that to other sorts of quit methods.....and it'll start to sound pretty good in terms of success.
Then again, ecigs aren't really stop smoking devices, and are certainly not marketed as such. They're more like harm reduction devices. They're meant to withdraw you from cigarettes, but not necessarily nicotine. And even with ecigs, it's not a magical road to quitting tobacco. Will power and desire to quit factors into it. If someone really really wants to keep smoking, and only tried ecigs to get the proverbial monkey off their back, they don't stand nearly the chance of success as someone who is really committed to giving up tobacco.
That's my two cents.