It's well over two years since I quit smoking and I'm largely detached from quit-line but I still pop in to the blogs over there.
I don't have any real stats, but I'm picking that far more people fail on each attempt than succeed. This CDC fact-sheet says that over 50% of US smokers attempted to quit in 2015. That smoking rates are only slowly decreasing means that only a relatively small number of quitters succeed each time, but given we all know of ex smokers who did give up after multiple attempts it's reasonable that people who try hard enough and often enough can succeed.
In my time there I've seen quite a few cases of people trying to quit using various methods. This time I used Champix, a brain receptor blocker, with other common methods being cold turkey, nicotine (NRT), and vaping. I think I tried everything except vaping over the years. Nothing against vaping, I was going to use it last time, but tried Champix instead.
When someone who is using the conventional quitting methods fails people tend to minimise that they were using these methods but when someone is using an unconventional method it is very easy to blame the method. I have noticed that people who are in the "not-smoking, still craving" stages of giving up smoking can often be very judgmental.
There's always been a divide between the people using the various methods with negative propaganda often aimed at the NRT and vaping schools by cold turkey advocates. Interestingly the most vocal opponents of vaping are often the ones who fail a short time later.
Occasionally someone who is a few hundred days quit will slip up and have one, when they try to discuss this and say they have no intention on winding the clock all the way back to day one they are pilloried by people who have only just quit and often are the same people who harass the vapists.
There are also some people who intend to quit but as a step on the way are radically reducing their amount smoked, for example from 45 a day to 1 a day. Some of the strongest invective I've seen on the site has been directed against people who have attempted to reduce as a step on the way to quitting. I don't get it, having one a day is a lot better than having 45 a day and if that is a useful step on going to being completely smoke free I fail to see the problem.
Of course, I feel they would be even better off having zero a day, but that has to be their choice. On the other hand, it is Quit-line not Reduce-line. The purpose is to get us off cigarettes completely. All of us there accept that we need to get to that point and encourage others to do the same.