I have more than a hundred applications installed on my computer, and only a handful of them exist in versions for any operating system other than Windows. If I used a Mac, almost all of these applications would not be available to me, and the situation would be even worse with Linux. Since I base my choice of operating system on the applications I wish to run, Windows is the logical—arguably the only viable—choice. Not only do these applications generally not exist in versions for any other platform, but there are no suitable substitutes for them on any other platform.
And are you trying to say that there aren't equivalents on other systems for the overpriced Winblows software you use?