Well, I can try and answer that question.
To begin, authors aren’t required to keep their games “under wraps,” at least not past the 10k (chapter two) check-in. If we’re going to spike a game, it’s usually at that point or before. But once the team has reviewed and approved that amount of material, the game is going to get published in some form or another. (So, @HannahPS, if you wanted to start a thread for your game, you’d be welcome to. 
)
But then you have the question of “why don’t they?”
I can’t give a definitive answer, but let me float some possibilities.
- It’s overwhelming.
You folks are a lot. There’s a lot of you. You have a lot of opinions, and sometimes you state them very forcefully. Moreover, how to tell who’s right and who’s wrong?
- They just don’t think to.
This is a real possibility. Most of the people we’re writing with are book-authors, not game-makers. Book authors don’t have interactivity to deal with, or beta testers, or game design, or any of a host of other aspects involved in producing a CSG. They might simply not realize how active the forums are, and how to make use of them effectively.
(And, becuse of #3, we don’t push them to.)
- It’s not remunerative.
XoR did very well, don’t get me wrong. But did it do so well as to justify all the time that Joel sunk into it? Even more specifically, was the time spent adding features at the request of the forums remunerative?
Authors that are writing for a living don’t have infinite amounts of time. A lot of them write to word-count targets, because they know how many words they can produce in a given time frame. And based upon time frames, they can budget their lives, pay rent, feed themselves, etc.
Adding new features/branches based on forum-users’ requests does make better games, but that takes time. And if an author has to choose between a better game and feeding their kids, feeding their kids will take precedence.
In short, until we start paying more, there’s not enough incentive for most authors to really engage with the forums.