The reason is that reaching out and touching things is what comes naturally to humans. The mouse is a temporary interim device between typing commands via a command line interface and reaching out and directly manipulating objects on screen via the MPG interface.
The whole history of user interfaces has always been about making the ever-increasing computer power that results from Moore's Law work harder to make what's on screen look and behave like real-world physical objects. Look at how video games have evolved toward increasing realism. We crave it.
There will be many, many critics of the whole MPG approach. Theyll all eat their words.
3. The new generation of MPG OSs will kill off mice and keyboards.
There will always be variety in PCs. But each generation of UI has its natural form-factor. For the WIMP UI, the standard desktop PC has involved a screen, keyboard and mouse on the desk, with a separate CPU nearby.
The natural form factor for Windows 7 and the other MPG operating systems will look like a drafting table. The mouse and keyboard will go away, and the "CPU" electronics will be built into the back of a giant screen between 30 and 60 inches. It will pivot at the center of the left and right edges. It will tilt vertical for TV and presentations, and horizontal for "desk mode" where you can lay your physical books and papers right next to your electronic ones.
Generally, however, you'll use it in drafting table mode with the bottom of the screen at about waist high and the top of the screen at about head height when you're in your chair. Youll use both hands to grab, re-size, move, copy and interact with documents and other objects on-screen. When you want to write something, youll do the keyboard gesture to bring up an on-screen keyboard, and just type away.
The natural MPG form factor for mobile computers will be a clamshell design with a screen on both sides (one where the screen is located on mobile computers today, plus another screen where the keyboard is now). It will snap flat to form a huge single screen with a kind of "kickstand" to put it at an angle, or you can use it in writing mode and have an on-screen keyboard and touchpad on the bottom and your documents on the top (like today's laptops, but with virtual keyboard and touchpad).
Microsoft's demo included a standard laptop, with all the touching going on awkwardly on the standard screen. But future MPG-specific laptops will have touching going on full screen, or mainly the bottom half when used in clamshell mode.
Optional physical keyboards will pop out of both desktop and mobile systems, or connect via Bluetooth. They'll be there for purists, old people and others who don't like the virtual, on-screen keyboards. But the mouse will be gone forever.
Windows 7 might be great, or it might be another dog like Windows Vista. But mark my words, the next couple of years will usher in the next generation of user interface from Microsoft, Apple and the Linux community, and its going to be really, really cool.