Remember that with as many different systems as there are, NO ONE can make drivers that work on ALL machines. Not nVidia, not ATI, not Microsoft.
And how can Linux kernel developers do a OS that runs ( and runs very well ) in almost ALL machines and architectures? It's so easy: Open ALL the code and let the users free. Free to use, free to hack the code, free to make a good driver that works in almost ALL machines and architectures, like the linux kernel.
I agree with you... Microsoft can't do that, nVidia can't do that and ATI can't do that, BECAUSE their systems aren't free software, and their systems' source-code aren't open.
"'Free software' is a matter of liberty, not price. To understand the concept, you should think of 'free' as in 'free speech', not as in 'free beer.'"