Imagine Microsoft going chapter 11, who is going to keep your Windows XP authenticated?
The hackers :)
Secondly like it's been mentioned 100 times over, very few people care what OS they're using. Only people using Linux have made a conscious choice, everyone else is just using whatever came in the box.
Yes, people don't care what OS they're using, they care what applications they're using. An OS is only as good as the applications available for it, and it's capability to run those applications without crashing. Linux gets an A+ for stability, but totally fails for a lot of applications people need (for both work and play). Windows gets a A- for stability, and an A+ for applications.
Unfortunately people who do make a conscious choice have to stick with Windows regardless simply because the applications they need aren't available on Linux. I wish just as much as you that Linux could do everything Windows can, but unfortunately that's just not the case. At least it isn't, until the Linux distributions get some sense and stop fighting with each other and unite into a single distribution for a single modern target architecture (like 64-bit), and make it easy and fun to develop and distribute for Linux.