Comment by mothballed

Even if you presume it's obsolete, the fact remains the land was distributed under a model where it had to be claimed, developed, and irrigated for agriculture. The water distribution and well systems alone required for agriculture far surpass use for residential purposes, for example, but once you have wells and irrigation suitable (not cheap in the desert, and also valuable) for agriculture it may be more economical to just keep going with it. The momentum of that remains and the economic incentives aligned with those policy choices remain with us as to part of the reason why desert land is used as it is. The first developed use of land can have a lot of influence on what happens next, it's quite different from starting from an undeveloped state with pure free market forces on development.