Why are Computer Manufacturers regressing with technology?

Is it just me or is it a growing trend these days for more and more of the excitable and highly marketable to be using low end, often times single-core, processors of the past? Why did Intel and AMD even bother developing dual and quad core chips when we were going to wind up going back to single core chips, and even VIA processors?

I have no problem with this trend as they are extremely energy efficient, but why is the industry on whole accepting this technological retardation? Just think about it, there are tons of new budget PCs being released that are all using low voltage, low clock speed, single core processors, their processes and power requirements have just been shrunken from the days of yore.

However even in higher end devices its becoming common practice to use the slower, single core chips. Just today I wrote an article about a notebook being sold in the UK that was designed to compete with the X300 and MacBook Air but yet its running an 800MHz single core processor and selling for roughly $2000. UMPCs not of the Eee variant are also maintaining the usage of single core processors. Personally I remember the good old days where all the new products only contained the latest of technologies without regard for battery life, weight, or size.

In an age where cell phones rule the world it seems our foci are shifting from power and speed that we'll never use to its full extent to the more compact, energy efficient, and lightweight designs that we might occasionally max out the processing power on. A large part of this likely has to do with the growing trend to make everything web accessible, I mean when I can access one of the most resource intensive apps I know of (Adobe Photoshop) from a web page, what's the sense in carrying around a seven pound machine just because it has the power that I need to use Photoshop?

So I'm curious, what are your thoughts on the matter readers? Furthermore when do you think Intel and AMD are going to see this trend and start re-engineering their dual and quad core chips so they can be used in these extremely efficient devices? God knows although it's not a major concern, some of these machines could really use the boost of a dual core.