I think smokers can only discuss their own experiences, and what worked or didn't work for them. No-one is really in a position to start making categorical statements about "the only way to stop smoking". Allen Carr did that, but he also mentioned that he used hypnotherapy to stop, before he wrote his books.
Smoking is a form of drug addiction and it's complex, like most addictions, because we're all different. I know people who found it fairly easy to stop, cold turkey or with help from patches, medication or therapy; and others who have battled with it despite trying just about everything they could find. I also know people who gave up long ago and have never been tempted to start again, and others who still get occasional - completely random - cravings, like my son. Others are social smokers, they can smoke a couple of cigarettes at a party, and it doesn't cross their mind to smoke again for months or more, and some people only smoke one or two cigarettes a day, but most of us get hooked quickly and it escalates from there.
Allen Carr also wrote about going out on a boat trip during his smoking days, and realising that he'd run out of cigarettes. He just about had a panic attack at the thought of spending the whole day on a boat without any, and held his friends up until he found a shop and bought some. The funny part was that he didn't smoke any of them during the day, and could never really explain this, but lit up as soon as they got back on shore. I can relate to this. An 11 hour flight from the UK to SA without being able to smoke doesn't bother me, but I start getting impatient and irritable if I get held up at immigration or waiting for my luggage, because I can't smoke for another 10 - 15 minutes.
Anyway, all the best to the smokers here who are trying to stop. I'll let you know how I get on.