You do have to consider that for a whole lot of people, maybe even a slight majority of those who use smartphones, a powerful cellphone is good enough for their particular needs. Let's face it, all of us here (I presume) aren't representative of the average PC user. And for those average users, the portability and small size is useful to them.

For those of us with more high-end needs, a smartphone or laptop will never replace the good old reliable desktop PC.