This forum isn't really any different than any other on the internet. Many times those who post regularly for a while lose interest. Some move on to other sites. It's a very cyclical thing. I can now count on two hands the members who are still here and post from when I joined over three years ago. It's sad, but at the same time it keeps the discussions fresh as new members bring something new to the table.
I know for my part, I've been way more busy with life and don't get on every night like I used to. Since my wife went back to school, a lot of the responsibilities that we shared on any given night are more on my shoulders now. Which is how I want it. She needs to focus on school, so I'm happy to pick up the slack. It just means my time for recreational activities is lessened.
Just my thoughts...
-Jason