25 years ago (or even 15 years ago), I would have probably agreed. But I don't think that's true anymore; to my understanding, students in public schools are equally as likely to use Chromebooks as they are to use Windows or Mac machines.
Yes, the point was that the "you don't have a choice but to use Windows" market is smaller than ever, meaning that the slice of the pie that's "I want to use Windows or don't care what I use" is larger.