Well since I am pretty new around here I can offer some insight from that perspective.
1) Rare cars, even more so now a days. So there isnt that many of us. Honestly I use this forum to research typical problems and source parts.
2) Why is it for that reason? Well This forum has "that guy". There is one on every forum. That guy is rude, self-righteous and wants everyone to accept that he knows more than they do (even if he doesn't). Honestly its a disservice more to this site than you can imagine. I have been through tons of old threads researching information only to see him beat a subject to death trying to prove someone wrong and then just go on and on hoping for someone to acknowledge he is right. Its pretty pathetic. I got jumped on my very first thread by this person. How do you think that makes new members feel about this site?
3) For as long as the above situation in reason #3 has been going on, its fairly apparent no one cares to do a damn thing about it. So why would this encourage people to be more active? It doesn't.
4) I own a website.. its very busy during the fall-spring time frame but very slow in the summer months. Just the way it is, I know I have tons of stuff I would rather be doing than setting in front of the PC!
Anyway, that's my take. Like it or not, act on it or not... its not my place to dictate these things.