Some of the runs just don't get run very often over-all. Cape Westwind is a prime example. First 8-person Trial; no loot; needed to advance the story; but no HM or XM versions after, which it could be considered a "builder" run.

Some don't appear to have to be run, if you're not interested in GC advancement. DD and AV come to mind. I haven't done either of them; and I'm not sure I ever will. Maybe if I am feeling good, and also somewhat bored... later