So what's the cause of this? Well, it really comes down to people running the game industry who don't play games. CEO's and their lackeys aside, marketing departments blow tons of cash on events that are ostensibly meant to promote new games, but in reality expend a lot of budget resources on B-list Hollywood talent, flavor of the month musicians and circus performers. Make a good game and it will speak for itself! If anything all this sloppy advertising takes away from the games since it's money that doesn't go toward actual development.
It gets worse when you consider that this money obsessed mindset leads to games that are meant to maximize short term gains rather than cultivate the medium. To paraphrase what one successively Kickstarter funded developer said in promo video; the problem with producers is they're really just looking for the next Angry Birds. In other words time waster games with simple mechanics and low budgets, but high potential for quick profits. The ugly twin of this philosophy is stuff like Call of Duty which is more akin to a military themed roller coaster ride than a video game with its flashy spectacle but shallow game play (even by FPS standards).