Okay, maybe I'm unclear on what you mean when you say "part of the game." I think semantics are messing me up. To you, what is the difference between "the machine" and "the game."
The game is the game. The product, the art, whatever is in the package.
The marketing is the promotion of the game. The hype trailers, the dev interviews, the pre-release coverage, the commercials, the press releases, the release schedule, etc.
The machine is the combination of the above two elements working in tandem with the people in the press, the marketing department, the PR department, the audience, and the relationship between all of them in making some people money and entertaining others. It's "engagement" and views and user youtube videos, advertising budgets, sequel possibilities, sequel budgets, sales numbers, developer staffing and layoffs, opinion pieces, backlash, etc. It's the industry.
It's the machine because parts of it that were never meant to be entertainment (layoffs, industry news, etc) have become entertainment adjunct of the product that is being sold (though it only exists because a product is being sold). It's the machine because the press works (presently) with the pubs to act as both an adversarial component as well as a marketing arm to get the word spread out. They make money off of the source material (the product) but not directly off of the product. But they know that if games didn't sell, they would make less money. They need games to be popular to make money. The pubs need (sort of) the press to get the word out wider, but don't like it when they spread the word negatively. The audience is also engineered to be both the consumer and a new product themselves. Evilore makes scads of money adjunctly off of games by hosting a place for people to talk about them. Kotaku gets money by lifting controversies and glitch videos that are made by audiences and presenting them on their site, so that the audience can then see themselves reflected back. The pubs like it when this happens because it increases the word and helps "engagement" to sell more of the product. But they don't like it when it reflects poorly on them.
Every piece of the machine tries to make money or get entertainment off of other pieces of the machine.
It's a machine.
We hear way more about what's going on in the movie industry than we do in the game industry
I actually think the secrecy of a medium is dictated by how voracious the appetite for the material is.
People don't (or didn't, pre marvel) care that much about what studio was making what. People don't really care what the new Mattel toy line will feature. People don't really care about the new Penzoil synthetic.
People care A LOT about what Apple is making -> they are secretive
People care A LOT about the new Blizzard property -> they are secretive
I think there's a lot of reasons for the secrecy. I think most of it is because the audience can't handle it when things change. So companies don't want to show/push things that will change or be cancelled.
Just look at any thread about a cancelled game. It will no doubt be called MUCH MUCH better than whatever was released by the company.