Maybe too many forum sites, covering what really is, a niche market/hobby?
I also have an interest in sports car endurance racing (another niche market/hobby), and there are really only two very active forums, one based in North America, and one in England (the larger more active one).
Maybe some folks don't want to talk about what they have? I've only been around watch forums for about 6-7 years, and I've seen more guys stop posting and dissappear into the ethernet than have stuck around that amount of time.
Is there enough watch news to talk about on a daily basis? There's another watch forum that I've stopped posting in, because they're asking memebers to donate money to pay the mods with, and they're closing off forums, unless you're a "premium member" (paying the owner). They claim to be a friendly forum, but that doesn't strike me as friendly. And the most active members comprise about six guys.
I don't know the reasons, but many forums of many different types, seem to be drying up.
Just putting some ideas out there...