Around a decade ago Microsoft introduced the tablet computer. A lot of us predicted that it would form the basis of PCs to come, that pen and touch would supplement the mouse, touchpad, and keyboard and that future PCs would be defined by all three interfaces.
However, the Tablet PC never really made it out of vertical markets, it didnt define the next generation of PCs, and it wasnt until the iPhone and then the iPad that touch screen monitors seemed to get the interest of the masses.
Microsoft made three mistakes. Lets take each in turn. All are based on not understanding that people resist change and need to be dragged into doing something different. Microsoft isnt alone in missing this -- IBM has made this same mistake and it was one of a number of reasons OS/2 failed. And Apple itself made this mistake with the predecessor to the iPad, the Newton.
The first mistake was to allow the proliferation of clam-shell tablet computers with keyboards. This was a mistake because users werent forced to use the tablet function in the computer and gravitated back to the readily available keyboard and touchpad. This form factor became the most popular, but since the tablet capability was rarely used they were simply heavier and more expensive laptops that often had a hinge that was either over-engineered or prone to failure. Most folks who used them went back to regular laptops for their next PC purchase.
The second mistake was to not change the user interface to adapt to the new input method. Even if you used Touch or a Stylus the Windows UI was designed for a mouse and was awkward for touch. This mistake carried over into the Windows Mobile platform and was one of the reasons the platform wasnt as successful as Apples. This is being corrected with Windows Phone 7 but by not changing the interface people werent attracted to the new input method and gravitated back to old form factors.
The third mistake -- and the one Steve Jobs indicated he is moving to correct -- is that the user experience didnt gravitate to monitors, so even if you got used to it, if you used a large monitor with your Tablet you had to go back to using a mouse or touchpad and keyboard. So you didnt reinforce the new input method and it was less likely to become a habit. The end result was that that Tablet didnt take off.
Apple first introduced touch in a cell phone in a market where they werent currently active. If you wanted an iPhone you had to use touch, there was no keyboard or mouse to fall back on.
Even so, initial volumes were a fraction of what they became and many folks who used Blackberries still preferred, and still prefer, a keyboard. Showcasing the problem didnt go away, it was simply a weaker problem with this class of device. They passed this to the iPod, which had no interface; this increased the breadth of people using touch. They waited until they had a large enough group comfortable with touch before introducing it into a larger device that also did not have an included keyboard and was difficult to use with a mouse. People do use keyboards with the iPad but they virtually all use touch instead of a mouse to navigate.