Just an observation not based on taking notes or charting stats
Each fall several newish brewers drop by with a question. Very few of those post more than two or three times. Occasionally one sticks around.
Probably the vast majority of forum members don't post, or haven't in a long time.
The core group of daily posters, which is maybe 25 people?, seem to be also pretty active brewers. Some are pros. A few own breweries. A few are notorious home brew living legends, authors, speakers. Most of the core group are consistently brewing above average beer and in multiple styles. Some brew consistently awesome beer. All of us are actively learning, regardless of level of accomplishment.
Life outside the brewery, a lot are technology pros, engineers, and use some form of science at the day job. A few are from all walks of life with no discernable pattern related to brewing.
Its hard to say how the forum reflects regular average home brewers, if it does at all. I suspect it's not the same, in that by default an internet forum may atract more desk job techy folks. But I do suspect that if we could line up every home brewer in the US that at least half are one and done. Someone bought them a kit, or they did out of curiosity, and they either never got around to it, or never brewed a second time. The percentage who brew at least monthly and for multiple years... very few.