That's likely because DNF is larger and less buddy buddy vs other forums with active chats, i.e. DS.
At DS (though seemingly much less active and slower overall vs DNF) there is a relatively small group of very active posters (perhaps about a dozen or so) plus the 3 Admins who heavily participate in Chat.
Whereas here (compared to DS) it's a larger and far less personal and closely alligned circle of 'friends' with mutual interests. The Mods also seem to be more active at DS, especially in regards to regular chat participation. It could be becasue the 3 Admins at DS are actually Owners vs Mods.
At DNF the ownership particiaptes little on a regulat basis, relatively speaking. Not to say there is anyting wrong about that, just a different way of owning/running a forum (at DNF it appears the ownership prefers the members do most all the posts). All that makes for inactive chat, with little hope it will become more active, IMO.