One reason--probably not the main reason--is xenophobia, or nationalism (depending on which way you want to spin it), tinged with a universally-held low opinion of Chinese exports. Good ol' American-made quality (or Canadian-made, or UK-made, or French-made, or German made--did I forget anyone?) certainly enters into it.
Although the Chinese have certainly muddied their own water so far as global perceptions of their exports go, on at least one point you've got to give them their due: they invented these things.
And my Riva, so far as I'm concerned, compares favorably with any mid-level PV, regardless of its point of origin.