An underappreciated aspect of all this: how many people are under NDA?
There's no upside to me talking about my current work and I might accidentally breach NDA, so I don't. I feel I can give detail-stripped war stories from previous jobs, though.
(Working on WinCE was very much being a "dark matter" developer, because there's almost no user community at all. And a good example of the NDA problem: you get some of the source to Windows CE, which you can't really discuss in public because it's copyright Microsoft)
Or they have security clearances etc. I'm sure I know quite a few people who go "Hmm. My employer doesn't even really want us posting on social media so on the one hand maybe I can earn a few Internet points. On the other hand, I could get fired. Tough call. (Not.)"
I worked for 3 years at Ab Initio, a software company with an ETL product which is - honestly - phenomenally good and worlds above anything else in the space, open source or not. (It was designed and is still mostly developed by graybeard former Symbolics and Thinking Machines Corp. hackers.)
And I never blogged or spoke a word about it, because it's absolutely forbidden both by rule and by company culture.
Given they make money hand over fist... I think they're doing just fine with their current strategy. I obviously can't give details, but they basically print money.
Many of those corps also have restrictions on speaking/posting publicly as well, and something like setting up a blog or Youtube channel would need legal approval. Some even ban public posting on social media and forums. These restrictions are not just on confidential content as well, but on literally anything you post publicly (as it may affect how others view the company). Due to IP agreements anything you post is also considered corporate IP anyways and thus even commenting on social media is forbidden.
Therefore if you see say a Github user who hides behind their screen name, or a HN commenter who purposesly keeps their job details vague, that could be someone who doesn't want to be dark matter - but the company policies force them to hide that way.
There's no upside to me talking about my current work and I might accidentally breach NDA, so I don't. I feel I can give detail-stripped war stories from previous jobs, though.
(Working on WinCE was very much being a "dark matter" developer, because there's almost no user community at all. And a good example of the NDA problem: you get some of the source to Windows CE, which you can't really discuss in public because it's copyright Microsoft)