Adventure games tell stories, and to do that adventure games create worlds. A game world can never feel alive unless it can be interacted with in some way. It doesn't have to be a video, it doesn't even have to be something that changes the game, but it has to be *something*. If you only allow your player to do things that immediately affect gameplay (though these are obviously the meat of the game and its interactivity, and the more you have of them and the more varied they are, the better), you will have a world that is functional - but not alive.
People are yearning for the ability to freely move around the gameworld, looking at objects from every angle, opening every drawer, manipulating everything they see. This goes beyond 3D games as they currently are, or likely to be for some time yet. They (or some of them) want a wider range of actions like jumping and running and pushing. Immersion is the name of the game (or mimesis if you don't like getting wet.) Realism, the game making you feel you're actually there, virtual reality, enter the matrix. That's a valid viewpoint, and no doubt there are great 3D Adventure games to be made. But there is still a niche for slideshow Adventures. They still have value. Some reasons why.
My User Contributions master list - my initial post links are down but scroll down page to find list to active links
