There have been. There were a bunch of Asian prostitutes at one point in S5 (I think), though we mostly only saw them running in terror away from some monster or ghost. And there was the befuddled Japanese chef from Party On Garth who I thought was kind of awesome and wanted more of.

...I didn't say there were many Asians on the show besides Kevin and co. But there are some.

This makes me want to know how many Latinos/Latinas there have been.