I will give you my view and it somewhat reminds me of what I was given when I asked this question of a few old hands when first joining and during being a mod myself.
First I don't go to any other forum. This is my only regular forum for anything.
Second getting onto this forum had made me realize over the years the value of any forum on any topic. Problem with that point is its kinda like online shopping. Once you get used to the idea and use it and experience success then what the heck you use it more and more. So shops now don't see me much at all.
But that means I have been able to address many other issues that have bugged me or I wanted to get out the way etc such as car repairs etc and checking and researching various things and these have stolen time.
Time is the other big thing. I get involved in all sorts and have way too many things that interest me and business activities. I did think being an empty nester was going to leave me more time for hobby or leisure activity but it has not turned out that way so I find time is getting scarce. In my case winter was not fun with an unheated shop. Even after spending coin on a couple of heaters. I have rust coming out the ying yang now in my shop due to the couple of times I got in there and heated it up. The heating and cooling condensation creation was killing me to watch so I stopped. I spent so much time wiping things down even the non rusting stuff just to get the moisture soaked up.
Then the other big thing I find is what used to take me a few minutes now seems to take ages longer. I dunno sometimes more knowledge or information on something seems to create less productivity. I blame all of you for this, you guys educated me. LOL Now I cannot go back to my old ways and do whatever it is in an adequate way.
IE I cannot work with a blunt tool. just for one.
I am really hoping summer changes this for me. Given it will be my first summer in the new place and with no move or house to maintain or fix up for sale. So I should theoretically get more time for shop but......I got quiet a load of business activity on the go so I dunno.
This brings me back to the single line sum up that I think it was Vaughn explained to me years ago......life gets in the way and it goes in waves and so you get more and less time for things like hobby and forum.
One last point that I think kills participation. Mobile devices. Note I said participation. Its easy to follow posts and the forum using the apps on mobile devices and yes a one liner reply is easy too but not always possible if you just having a quick peek while waiting in a reception area in my case. But actually making a post etc and posting pictures can be easy but its the typing that aint. Not looking at excuses just trying to explain.
I guess some guys also do not like the amount of off topic we have as a site and probably want more pure woodworking and posts that do more to stretch the bar.
Speaking personally I really like everything about our site I dunno how people that frequent many sites manage to keep any kind of meaningful relationship going with many thousands of users. I actually like the fact that we a relatively small bunch and it kinda reminds me of the sailing club I was involved in back in the day. We had 150 paid up members but something like 30 active attendees at races and events.
My to do list in woodworking is so darn long I also don't need more stimulation to make it longer. Would be happier right now if I could work down the list and be posting my progress. I also blame GLENN. (only joking Glenn) he has me sworn to organization before any more playing. He had nothing to do with the pledge it was a personal thing I did after many of his Bradleytizing posts. LOL.
That's my story/explanation.