Buck, land is at a premium out west, and you'd be surprised what passes for livestock acreage and horse shelter out there.
I agree; it doesn't provide shelter, but then, it's not meant to. It's only meant to contain the animals.
Turnout usually consists of a dirt lot, or if the horses are lucky, an area 1/2 acre in size or maybe a little larger.
Horse keeping in CA, TX, and AZ is nothing like how it's done in other parts of the country.