Sandbags have long been used for creating strong, protective barriers, or for flood control. The same reasons that make them useful for these applications carry over to creating housing: the walls are massive and substantial, they resist all kinds of severe weather, or even bullets and bombs, and they can be erected simply and quickly with readily available components. These days polypropylene bags are used for superior strength and durability. For permanent housing the bags are covered with some kind of plaster for protection.
There are additional advantages:
-- All materials can be purchased for less than it would cost to build the same structure of brick or adobe earth.
-- Learning the craft of earthbag building is simple.
-- Because earthbag homes have less thermal mass, they overheat less in hot climates and balance humidity levels more efficiently.
-- Earthbags are earthquake proof.
There have been a few permitted earthbag homes in the US and hopefully we can step up progress to have them codified by the authorities.