There's no point whatsoever in those pre-rendered trailers. It almost accounts to false advertising if they didn't have that tiny, almost missable 'not in game footage' note at the bottom of the screen.
Many games can make trailers using in game footage/cutscenes so it makes those pre rendered ones all the more jarring.
It's just for hype, really. It's no different to movie trailers - how many trailers have you seen for films that paint a completely different picture to the final product?! I remember when Sweeney Todd came out and not a single trailer I saw even hinted it was a musical. I don't mind musicals, but I have to be in the mood for them, and as I wasn't expecting a musical, I got bored within 20 minutes - I also wanted to smash Helena Bonham Carter's face in, but that's just because she's annoying as hell.
Remember the old 'trailers' for the release of the PS2 by David Lynch?
That told you absolutely nothing about the console, it was just all hype and marketing.
I thoroughly agree that companies should not be allowed to release trailers for any form of media that are not true representations of the final product.
It doesn't look that different from in game graphics these days except for the iffy camera work. The reason it's prerendered is they work on the performance of the game throughout the development of the game, that isn't showable until it's done.
Of course it is for advertising, you misunderstand me. When you see a movie trailer, it is different because what you are doing will be what you are doing in the movie, just watching.
However, video games are meant to be played. So why are there some trailers that have no gameplay footage, or even game trailers that have real life action to where you do not even see ANY form of the game?
These are similar to those commercials that show you a car for 1 minute and it is a commercial about toothpaste. There is really no point to those commercials.