Because the truth is that Microsoft and Intel have attempted to push this concept for years - and they pushed at a door that hardly opened.
Despite repeated attempts by Intel to do attractive looking reference designs and a number of PC vendors giving the concept a whirl, tablet PCs only found themselves in niche applications.
Useful, perhaps, for nurses and doctors to make notes on, or for aircraft engineers to do the checks required, the Windows implementations of tablet just never sold in the numbers that Microsoft had predicted.
And there's the rub. Apple has consistently bested Microsoft and Intel on reference designs for products - its products do look classy and have a classy price to match too.
If Apple does successfully introduce the "iSlate", and it does well, it's the equivalent of Steve Jobs socking it to Microsoft yet again. It will be yet another humiliation for the Seattle giant.