It's already fragmented enough. If you only have one fragment of an interest, a special forum is ideal, but for those with broader interests one has to hack all over the place.
Also, part of the reason specific threads lag is because they aren't interesting, a lot of the touring specific threads are very specific to a particular place, and often the person is leaving so soon that before the thread has run it's course they have gone.
I'm not sure the criterion for a new forum should be that currently the posts have minimal interest. Unless it can be demonstrated that is only because of format.
We already have a separate location for touring stories. I like well writen touring stories. I may never go to Argentina, all the more reason to read about it. I'm not going to be very interested in a thread on the best place to get water in Argentina, not only don't I care, but I doubt many other people do either. A thread on what tires to use in Argentina, may quickly define itself to a point where we can all pile in with suggestions of where best to buy cheap nobbies.
Crazyguyonabike already seems to be outbidding us on the stories. Such that already having a forum on that subjects just ads to the impression nobody actually gets out much.