[mikestew]

It is very often a zoning issue. "Manufactured" housing, which I'll use as a blanket term for anything not completely built on-site, is often equated with "mobile home" or trailers. In the U. S., at least, mobile homes have a stigma that carries over to manufactured housing. IOW, mobile homes are for poor people, and you're not poor, are you?

Consequentially, manufactured homes often have to be built in unincorporated areas which don't have zoning restrictions.