Why do all audio forums on the internet seem "dead" ?

Are you talking all forums or just Audiogon?

I agree with jafant, many more choices out there these days for a dwindling audience.
Audiogon forums are heavily moderated, many choose to go to other forums, where more freedom is allowed.

AudioAficionado
Audio Asylum
Audio Circle
What's Best Forum
Audiokarma
AVS Forums
Steve Hoffman Music Forums
Head-Fi
diyAudio
USAudiomart Forums

Just to name a few, and these don't include any social media sites.

I do think general social media, non-audio related, also has something to do with traffic slowing down.
Audiophiles are a dying breed, like it or not. Even those left have more and more distractions pulling at their free time.

Many of us left are in our 50's, 60's, and older, still recall when audio had a very central place in our lives. Before social media, Netflix, cable TV and VCRs. There used to just be audio and a couple of TV channels to compete with free time. It seems like now we have less free time, and more distractions fighting for the little free time we have.