Well, they aren't to each other and to the team. But they have to control the information fed to the public on their game. That's how one game developer answered the question on why some folks feel the game development process is kept away from the public eye.
The person goes through four very good points with the last really being a big one. There's the usual process of trying to make a really good first impression, marketing timing, and trying not to piss off the fans.
The fourth one though, the fourth one is the one that hits home, especially for me who is a software developer. We all like to think we know how things work, but we really don't a lot of the times. It's easy to say you can do this or you can do that. Lord knows I've heard that plenty of times in meetings before I was even consulted. Sometimes even the simplest things aren't so simple when trying to turn an idea into a code.
I worked at a few financial institutions, but I would never understand the processes fully. I can get some basic ideas, but there were plenty of times where what I thought i knew about the process wasn't at all how it was done, even if it made sense to me. Conversely, I've learned over the years to really simply my explanations when trying to explain what I've done to certain groups of people. They don't want to know all the boring details on how I achieved a certain milestone in my coding. They just want to know if it was done, and perhaps some very high level detail on how. But they will most likely never know what went on in getting to the end goal. And it's not uncommon for people to fill in the blanks on how everything's done with something, anything, that makes sense to them. We all do that though, when we think this is how something is done, rationalize it in our minds, but then it's truly not how it really is.
In the end, the industry isn't trying to keep everything secret from you because they like to. They are just trying to manage expectations and generate interest in their game as well as not show anything that will probably not make it in.