First, there were not EVER 40,000. We hadn't even broken 10,000. Second, there may only be a dozen or so logged in at any one given time, but that is fairly meaningless. This is not a real-time chat room; users simultaneously online doesn't really matter.
Plus, I think we'd all rather have a few QUALITY posters than a ton of pointless drivel. Many of the registered users on the old boards were there as an influx of "refugees" from when IGN went to their pay model. I don't think we miss a lot of what happened at that time.