Actually for the southeast, it's the preferred foundation, due to the humidity. It's cheaper because of less labor. No piers, it's more solid than a crawl space and the horror stories everybody has heard about slab foundations are the ones where people didn't use plastic and gravel under the pad and it was before pex was invented. My builder builds them all the time and says he pulls in an extra pex water line. Keeps out rats and bugs, spiders like it dark and damp.