People don't use Windows because it's a "fantastic" OS for their needs. It very evidently is not "fantastic" (or anywhere close) for anyone's needs but Microsoft's. People use Windows because it comes bundled with their PCs due to Microsoft's monopolistic malpractices, and because they can't get bothered to figure out how to get rid of that bloatware / malware (or, they would get rid of it if possible, but are held hostage by the software — or malware, e.g., Adobe — they need to work only working on Windows, again due to said monopolistic malpractices).