Becuase MS make 10 Billion a year, and give home users a hard time with licencing, support and products that no one really needs unless you have to have shiny things and DX10.
Home computers used to be cheap and easy until these goons took over.
They were the first and ONLY company who were able to develop and sustain a viable OS that supported hundreds & thousands of different pieces of hardware in various combinations. They have no problem taking advantage of this by charging outrageous prices to you and me, and making sure they get their cut by releasing a must have upgrade every 4 or 5 years.
At the end of the day, they are the only solution that provides a working, all-in-one easy to use PC package that your granny could pick up in an afternoon. The only real alternative is Linux, and even in easy-go-happy formats like Ubuntu, it still doesn't compete with the Lego easy shiny fuctionality of MS's products.
Not only that, Windows provides everything you need to get going. You don't need to choose or download a media player or web browser. Its all there out of the box - off you go.... easy as that.
In colusion with the likes of Dell, Gateway, Intel, Norton, AMD, ATI, Nvidia, Creative, game companys etc, MS have built up a virtual monopoly that can't be broken. You must have Windows.
One day, Linux will be a great alternative - when it is easy to set up and run by clicking your mouse a few times. But all that command line techy stuff has to go out the door. It NEEDS to be pretty and icon-clicky-easy. Otherwise the public won't bother. Far easier to throw some $$ at MS.
The biggest failing of Windows is its size. Its not a pure OS anymore - full of useless bloat that drives the price of hardware ever upwards. Its now a PC running, security managing, multimedia playing, office running, world communicating, toast making monstrocity that rules your CPU and hardware. MS and their partners love it ($$$). We tolerate it because we have no choice.
What ever happened to Load""?