Summary: The allure of the iPad enticed millions to buy one for fun. The discovery that it could do everything desired outside of work led many to forget about using Windows outside of work.
Microsoft saw this coming and radically changed the design of Windows to work on tablets, desktops, and laptops. The folks in Redmond saw the writing on the wall and knew they had to change the OS into a tablet OS to keep Windows in the home. They already had the enterprise locked up so bringing Windows to the tablet was an effort to keep folks using the OS at home.
iPad: Kicking Windows back to the office | ZDNetMost of the folks I interact with about Windows on tablets who like it, and are excited about it Windows 8, are those who either make a living in the Windows ecosystem or have a special need for using it outside the scope of typical home computing. Having full Windows in a tablet form is just what they need to do what they want both for work and at home.
Unfortunately for Microsoft, there aren't enough of thos enthusiasts to make a difference, as proven by the Surface RT debacle, and low Surface Pro sales (compared to the iPad). The vast majority have already been shown that their beloved iPad is all they need outside of work. The iPad has totally replaced PC usage in the home for many owners and kicked Windows back to the office.