For me it's a combination of the logistics (models/participlants / space / cost) and wanting to keep my identity guarded.
The industry I work in during the day is filled with people who are more than capable of searching the Internet to depths many would not even think of.
As people here say, this wont make you a decent living - so as that's not the case I need to ensure my reputation in my day job stays clean .
Shyness, lack of technical knowledge on lighting/filming, worry about bringing strangers into a home studio, (currently) significant other, and most of all no clue how to even begin making vids. I've entertained the idea, and it would probably be good for getting over my shyness, but never followed thru. Maybe someday, maybe not...
I stopped producing when technology evolved such that I could no longer defend myself against piracy. Originally, if you degraded a VHS tape a few generations, the next generation would be too poor a quality to have to worry about it being pirated. The digital age changed all that.
So for me, it's hard to get up to invest all the expense and effort only to see your work given away for free over on VK.com and have to give Russkies way more personal information than I would wish to get it taken down only to have it reappear on a BitTorrent that you can't get taken down.
Having dabbled in production, its a complicated area. Having a suitable space is critical - a few scenes have been shot in my tiny flat as an add on to a session (giving the model a free scene) the limited space restricts how you can film and what you can do. Shooting a two person scene is pretty much impossible and there's not that many ways to do self gunging scene! I certainly don't want to be wandering in the shot, I'm not even happy being heard! I'm not the best cameraman nor the best Editor nor a publicist - all rather important things.
Combining the skills and resources of a few people is probably the way to go (although they can go wrong - there are "missing" GM scenes for example) Perhaps a group of people as a cooperative could jointly run a studio, equipped to meet the needs of WAM shoots. Interchangeable backdrops and good lighting with the ability to use height for added effect would allow a number of scenes to use the same space. Indeed there would probably be slots available for group play events. Of course the initial investment needs a pot of money so it's probably going to stay on the "when I win the lotto" list.