I thought the article was dumb, I mean the second they said, "you can get better gaming running windows 8 with wine or windows 8 using boot camp or parallels" , I stopped taking it seriously. How is virtualizing an OS going to run it faster, and boot camp is the same as running native windows 8, but on a mac so I don't see how that's any different than a PC. Also, WINE, might be debatable, if you can get it to work, good luck getting the average user to try and figure that out.
Anyways, windows 8 is popular because as 123danny said it, backwards compatibility to legacy software. I'm an engineering student and I can run all my programs on my tablet, very useful for me.
The Other major reason I feel, is its a "full" OS. Not that android or iOS aren't but for example, ie runs flash natively, I never have to worry if something in a website will not work, versus using android or iOS, yes it rarely comes up in them too, but when it does, its a pain. Also Office, and many more productivity apps make it so much better.