well, the thing is that a lot of people here have more responsibilities now than they did when they first joined. I, for example, have a full time job now, so I have considerably less time to post. another thing is that interest fades over time. the fact that as many people have been here for as long as they have is quite amazing actually. That's because these kinds of forums of this size don't usually last this long. I've personally lost quite a bit of interest in the pony scene honestly. I'm still very much a part of the fandom, but my drive to be making stories on this has waned considerably over the last 2 years. we can't force people to remain interested or to become more active. Personally, I'd rather see something genuine and short lived than forced but lasting forever.
That said, It would be nice to see people coming back. I always think back to when I first joined and the chat was full of laughter. people have gotten considerably more sensitive to jokes that come out wrong and a little frustrated at each other, and that's a real shame.
Another thing is that this forum is pretty old. It hasn't been rebooted in... well, ever. The design of the forum has stayed the same (save the subforums) for the past 4 years or so. it doesn't help that every time we try to reboot this place and update it, it's met with anger and controversy. remember when we changed the look and half the members left? It took almost a full year for that controversy to come to an end. So Quite frankly, I think a lot of the staff has gotten tired of trying to reboot this place. every time we've tried, it's just angered everyone.