There are not enough people in an American metro area to distribute this variety across stores across the area. The produce departments sell what the computers

There are not enough people in an American metro area to distribute this variety across stores across the area. The produce departments sell what the computers report as margin friendly. There are enough people in a metro area who want this and are willing to go to the asian district to get it. The five or 20 families in a subdivision who want this are not enough for all the Safeways and Krogers in the subdivision to stock this food. But enough handfuls of those families across the area are willing to go to the few stores concentrated "in the asian district" to make it viable for those few stores. This is also capitalism at work. Huge markets and niches both have ways to operate. As for tracking and safety, as others on this page have noted, knowledgeable (and alert) shoppers and proper preparation go a long way to promoting food safety at the end-use end of the chain.