Because Apple doesn’t have a large R&D department like Microsoft, Google, Intel etc. and making something like Windows 8 would have been too lengthy, complicated and expensive for them. Apple is an image company that has sheep-like followers (including the tech media as a whole), so they tried the simplest, quickest and least expensive solution (adapting a phone OS to a tablet) and it worked. Look, Apple could make an iBookend that does absolutely nothing, but as long as it has a shiny apple logo etched into it, some people would still buy it for $200.
If you start to attach mice and keyboards to a tablet then you don’t have a tablet anymore, you have a notebook.
That was just an example. If people can get by with the tiny touchpad of the MBA, they would be MUCH more comfortable with a 10" screen.
The finger argument was a simple test how it will look like if you want to edit 1/8" sized icons and buttons with a 2.5" sized mouse cursor.
First of all, most Windows tablets come with digitizers, especially the new Bay Trail models. And secondly, if the tiny touchpad of the MBA is sufficient to handle a DAW, then why would you consider the MUCH larger area of a touch screen insufficient? It makes no sense whatsoever. Heck, the touchpad of EVERY laptop ever made is still much smaller than a 10"" screen. So, that’s why I hypothesized that behind what you say there is something irrational, like an irrational hatred for anything Microsoft (which is typical of Apple fanboys, you can’t blame me for making the easiest assumption.)