People do not want touch PCs. It's really that simple. Microsoft is trying to move the market in a direction that it doesn't want to move, and the market tends to react negatively to that.
Metro on a desktop PC is fucking awful. It's best used like Windows 7, where you try and pretend that Metro doesn't exist. In that case, why wouldn't I just use Windows 7? It's not much better on a laptop. The UI is just not built to do real work. It's built for phones, and it works fine for that. When I'm trying to do my job, it's something to fight with as it decides that I really didn't want three windows visible at once.
"Windows 8 - almost as good as Windows 7!" isn't much of a marketing slogan.