Only gaming notebooks have a Core 2 Extreme. Toshiba X305 has got it. Dell's XPS has got it. Why not all new laptops ? Wouldn't it be better than Core 2 Duo ? Even if the Laptop is used for applications like Photoshop / Video Editing and Music Productions that use heavy VSTi's and samples.
I guess market research has found that most people using laptops don't require a high end device. I'm guessing the majority of laptop users are either business people that do general office work on them or students doing papers and some audio/video playback. These users may be more interested in weight/size, power efficiency, heat discharge, and other similar features. Performance is probably in there too, but not at the level that you may be thinking.