There is a full range of sizes in Japan, including the big fat ones and medium ones too (from Toshiba, Sony, NEC, Dell, etc.).
It's just that the range of ultra-portable and thin-and-light machines is much more developed over there, so consumers have had more features and designs to choose from in those categories.  A lot of people in the US have been paying a premium to importers like Dynamism to find machines that suit their needs, but recently things are changing for the better as more and more of those machines are being sold in the US.  In the article, Intel's Anand says even more of this class of machines will be available to US consumers next year.  This doesn't mean the current classes of machines will be going away, it means we'll have more to choose from.