a demo isn't needed when the name of the title already does the job

I think they are wanting the people to blindly purchase the game, not matter how good it is.

Often people doesn't like changes, and thats what they are most likely going to experience with GoW2.
Sequels can be tricky. People want new content, but not too different one. You get what I mean?

They are hoping the people are gonna buy it like the first one.