First off, I am 100% sure some people do "simply" grow out of their addiction. But what does that mean? What life changes happened during that period of growth that caused addiction to be a more manageable personal issue?
For me, most recently at least, it was when I simply could not find a vein anymore. I had always had poor vein access and after close to 5 years of IV'ing black tar heroin, I had more abscesses than I had available veins. Muscling tar is not pleasant, often leads to an abscesses at the injection site, and has poor bioavailability, but if you are sick and have spent 20 minutes poking yourself at least 20 times (hopefully going through 2-3 syringes in the process as well, and having to deal with backloading your dose), the option becomes more appealing. All of this poking around looking for a flash leads to abscesses as well.
With a lifetime of poor vein access, I was doing all the things they did to me in the hospital when I needed an IV: heated blankets, hydration, using alcohol swabs, tourniquets, at least attempting to rotate injection sites, and so on. When I discovered my hands and feet had slightly easier access, I was elated, but that only lasted a couple years, and it really, really, really hurts to miss in your hands and feet.
Is that what they mean by "simply growing out of it"? If so, I feel kind of insulted.
Eventually, after simply not being able to get high via IV anymore unless I got lucky, I did one last big detox (probably at least my 20th, including 2 in-patient ones), went back to my suboxone doctor, and have been stable on a low-ish dose of the sublingual suboxone for several years now.
In my recovery I have been to hundreds of NA/AA meetings and volunteered with harm reduction groups and this concept of "I simply grew out of it" is not a common theme. What is much more common are things like 1) I couldn't stand sleeping outside anymore, 2) I got pregnant, 3) I ran out of vein access, 4) I had a real opportunity to stop using and took it (like rehab or strong social support or job support), 5) I was sick and tired of feeling sick and tired, and so on.
Just to be sure, I am not saying "simply growing out of addiction" via "natural recovery" -- as the article discusses -- is not a thing. It's just not enough of a thing to warrant much attention on. A sincere congrats to the people who grow out of it (and, like I said, I'd like to hear more about what that growth process looked like), now let's help the millions of others who haven't.