The source of all evil...
A guy I know told me - whether this is pure gossip I don't know - that there are timer-like devices (bugs I think) within a Microsoft OS that are set to go off after a certain period of time, rendering it useless. Hence the reason why they don't last 'forever' and have to be replaced. That of course equates to more money. Sounds cynical I know, but I wouldn't put it past them.
Personally, I don't really have a problem other than the money strategies implemented; they get easier and easier to use and are good for non-experienced users. We only got our first home computer about three years ago (sitting a year or so of Standard Grade Computing without a computer isn't a good idea!), and I presume Windows XP was the reason why there was little 'catching up' to do.