If I go to a forum and I'm not immediately invested, I usually can't find any reason to go back. Turning visitors into lurkers should be the goal, and it's hard to make someone want to lurk with limited lurking materials. I'm going to give you guys an example of a potential forum-goer.
Let's say "Tim" picks up Skullgirls, kicks it around for a week, but can't quite figure it out. He decides to look for a forum, and finds us. He looks around, doesn't have any questions he's willing to ask, but can't quite get a grasp on how to play just yet. While he's contemplating sticking around and making an account, he decides to look through all the subforums (maybe he'll see something he can more easily understand) and finds the Chess thread. He's a big Chess fan, and enjoys listening to Isa talk about chess. He makes an account to leave a comment, then gets distracted on Reddit.
The next day he remembers he left a comment, so goes back to check if there was a reply, and there was. Before he checks the reply, he sees in the recent threads section a witty title for someone's Training Diary. He decides to click on it. He gets to know Gllt's, the funny thread creator's, struggles to git gud. And while doing that, he notices that Isa also takes part in gameplay discussions. Tim is still not ready to partake in gameplay discussions, but now, little by little, he's getting more invested in lurking in gameplay threads. All thanks to the off-topic chess thread.
This is the type of Skullgirls player that we will never see again. If they end up on Skullheart, they're at one point interested in Skullgirls. Shutting off avenues that keep them coming back is not good.