I've only been on HR going on 3 years now...so I don't know how busy it was 10 years ago in the Analog forum...but judging from how it was on other BBS sites that had "Analog" forums...it's the same thing going on everywhere now.
You can go to entire BBS sites dedicated to nothing but Tape/Analog gear...and it's not that busy like it use to be.
First off, there are way to many audio forums, and they've lost their initial "gee whiz" factor. Any/every audio forum you go to, you see the SAME topics, over and over, and over, and over...so people have just sort of gotten numb to it all.
AFA "tape" specifically...the user list is dropping off, and at the home rec level, you will not see too many newbs diving into it like they were when "digital" was still a "bad" word, and the transition to digital was slow.
Also....it costs a LOT, LOT more to run a more serious analog rig, with or without tape decks, though certainly, with a multi-track deck + mix down deck, tape makes it even more costly, 'cuz even a used, decent tape setup is going to cost more than some software app.
Anyway...there are enough folks (I'm one) who will probably be running a substantial analog studio for a long time to come, even though I use a pretty involved digital rig too. I just upgraded my DAW software, am buying some new hard drives and upgrading my PC processors...etc.
I think the niche group that wants to be all analog or all lo-fi analog at the home-rec level...is going to get smaller and smaller, though there's nothing wrong with hanging in there if that's what rings your bell.
While I only have a 1/2" Fostex G16 as my multi-track, I still keep an eye out for a decent 2" 24-channel deck, but it would have the be a really great deal, on a well cared for deck, and close by for pickup. I'm just saying, I don't have the "fanatic" desire for tape like I use to...though I certainly will continue to track to tape on my G16, and bump up to a 2" if the right opportunity came up.
Not sure if any of that answered the thread question...but in a nutshell, I just think it has to do with attrition...newbs are opting for digital, and there are less and less tape/analog users. Plus, once you have your rig dialed in, you don't get as involved with forum audio chatter, unless there's some really interesting topic that pops up...and there's fewer and fewer of those, since most things have been covered to death, especially with tape, since there is nothing new with tape and hasn't been in many years.