Most "serious" people in a hobby don't spend a lot of time of forums from my experience with several hobbies I am involved with. Talking about a hobby is just that and serious people tend to do less talking & more doing. There are always exceptions but my guess would be less than 5% of the people in the hobby visit any forum and less than 3% are likely to be active on a forum.
I sell used pinball parts on eBay and when I communicate with customers looking for something specific I don't have I tell them to post or watch Pinside and I would say less than 5% know about Pinside when I refer them to the site.
It is kind of a shame more in the hobby don't visit websites & forums because there is a lot of good information exchanged. But most people I know in the hobby just don't like dealing with the drama. I post & lurk here when I am taking a break from the real world but rarely stop by unless I am bored. These days it seems like Facebook (closed groups) are a much better place to hook up with the more serious people. I know a lot of people who were active on Pinside & RGP that have moved over to Facebook lately.