first of all, i assume you are referring to far-east asians. 80% of Russia is in Asia,Caucasus region as well, and the entire middle east, turkey Pakistan and India are also Asian. Its a huge continent, and there's definitely not one race that can claim "Asian" in the same way "American" race should include inuits, native american, WASPS, south americans and african americans.
now, to the main question, i think its mostly related to the beauty standards that "asians" want to project, and those standards being totally incompatible to western standards. This functions as a barrier to "asians" being considered hansdome as simply the "asian" beauty template is not attractive to westerners. For example, google hot japanese guy or hot korean guy, and you will be flooded with androgynous guys with poor wig-like hair, zero facial hair and facial expressions trying to look "cool" like zoolander.
As many guys have posted on this thread, there are some gorgeous east Asian men, but they conform to western beauty standards (stronger jawlines, short masculine hair, facial hair)