Since MSFT finally gave us an operating system that works well why should I buy anymore
window upgrades? Their old business model was better for the corporation "throw in some more bells and whistles but don't fix the crashing and freezing". Now that some #$%$ at MSFT let out an operating system that actually works they made it much harder for the company to sell their product.
Power users would upgrade to the latest O/S to keep a competitive edge and the wealthy would upgrade because they want to, much like some get a new luxury auto every year whether they need it or not.
Of course penguins who don't have anything to do but post at yahoo 24/7 could certainly get by without upgrading or even maintaining a PC of any kind by using the library PC's.