I think there are two sorts of members there - (1) audiophiles and (2) music fans in general (obviously with an overlap between them). I'm no audiophile, but I do love music, so I'm in group 2. For me I like hearing discussion about new releases across the spectrum of music, discovering old bands/artists that I didn't know as well when I was younger, and hearing differences of opinions about artists I like. It's usually fairly healthy discussion, and because it's a music in general board, it attracts more members than a jazz-centric board like this.
I don't think it's going to change there any time soon, despite bulletin boards being a relic from an earlier digital age.