I talked to a couple of TC'er recently about this exact phenomenon -- one person said that she had no idea that there was a TC forum, and she was very interested in checking it out. Another person said that he was active on "Wander the West," an exclusively TC forum, and did not have time for RV.net.
And don't get me started about my fellow TT folks -- when this subject comes up, very, very few of them have ever visited RV.net or Woodall's or Trailer Life, and they are just stumbling around in the dark, trying to reinvent the wheel, when they could be here receiving wisdom from the experts. That is certainly why I am here -- I have learned more useful stuff from the forum members than I learned in college, for sure. (Plus being scorched by the occasional flame, but that is the price I pay for sitting at the feet of the masters.) ;)