they can steal it
in US a large percent and in many other countries, majority of windoze installs are pirated. combine this with a wish to conform; and nice visual OS make it easy to use. novell went down the tubes even tho it was more stable as they didn't want to redo their utils visually.
(this is a marvelous book that explains m$ success and failures of dbase, wordperfect, novell despite -at times- good product):
In Search of Stupidity: Over 20 Years of High-Tech Marketing Disasters
by Merrill R. Chapman
Apress ? 2003 (268 pages)
ISBN:1590591046