Not every publisher uses the same strategy every time. I think it depends a lot on whether there's been any major studio changes in the dev team of a given game and any major changes within a given game series. For instance the Hitman series underwent both changes, which is why I think Eidos chose to let players know well ahead of time what they were doing with Absolution via example gameplay footage. They probably knew some of the long time series fans would be upset with some of the changes, and that they'd have to count on bringing in new players to the series. It seems to have worked for them, and while some long time Hitman fanatics were pretty upset, most seemed to roll with the changes, myself included.
Another example is Sleeping Dogs, which underwent HUGE changes. It was not only quite a departure from it's original True Crime series roots, it got a new publisher midway through development with an extensive graphics makeover, and was developed by a new dev team assembled from developers from prior teams. They wanted to make sure fans knew about the game and that it wouldn't just be another True Crime, or another GTA. They needed to showcase the differences via gameplay footage. While their sales weren't as high as anticipated, they later said they probably had unrealistic expectations, and that overall the game was definitely a success.
This kind of extended advertising well before launch can be very effective and doesn't even have to cost much. All they really need do is get out there and get involved in interviews and post gameplay footage snippets on their own site or YouTube. For the most part though, advanced pre advertising is not only unnecessary, it can also reveal too many secrets to competing teams.
