Microsoft understands this and, quite frankly, doesn't care. They know that when the average consumer buys a new system, they'll take whatever OEM OS and software is bundled with it. That is how Microsoft corners the market and that is how they assure their anti-competitive practices will remain intact.
Windows Vista will make it into your home. The only variable in the equation is when. And you can bet that it will precisely coincide with your next PC purchase. Microsoft has seen to that.
Except that I don't buy PCs, I build my own.