First, I think this is one of the most polite boards I read. There have been a few heated discussions, but I've never seen an all out flame war raging even on highly charged topics like firearms in the park.
As for the kiss and tell, I appreciate it. There really are very few "secret" streams in the park and I think the really delicate ones are pretty well protected. I never did understand the "caught this in a secret stream" stuff.
In all reality, in the park, the general advice of "find a stream, hike 30 minutes off the road and start fishing" is pretty sound and often repeated.
I would venture to say the reason is as has been stated before, some interests change, some move on to other things, some get busy with life, and some may leave angry but given the nature of this board would make it unusual for someone to leave angry.