lets admit this, desktop market will be almost non existent in the future(only gamers and software professionals will require the power of a desktop/workstation). Also Budget consumers will most likely stick with the desktop model like institutions(ex:schools and other small/big business that need basic computing for productivity)
Soon our phones and tablets will connect with peripherals(monitors,keyboards,mice,etc) and be able to fulfill most of our computer needs without any or little lag..
Windows wants to make sure they are the OS of choice when it comes to that, it makes sense they design Win8 how they did, unfortunately most of us wont be willing to make that change just yet.
plus windows does not update their OS for at least 3 years(will probably change soon), they need to prepare for the FUTURE!