The term "Wagon Train to the Stars" had more relevance than we thought. Much of humanity has gone to outer space, but apparently all the planets they could settle on were dry, desert-covered worlds. A big advantage to setting a sci-fi world in a desert is that it's easy to conceptualize, compared to a geographically and culturally diverse world like Earth. The author doesn't have to spend time explaining the history or nuance of the world because there is none. Also, judging by the planets we've been finding around other stars in recent years, while potentially habitable planets seem plentiful, earth-like ones seem slightly more rare, with slight variations in size, composition, and average temperature making the difference between an Earth-like mixture and a comparative ice world, water world, or desert world. A moderately large galactic empire would almost certainly put up at least a token effort at setting up outpost colonies on some of the less pleasant worlds, if just to have a place to put your Landfill Beyond the Stars. When life becomes hard, and on such a world, it usually is, morals are the first thing you throw away. Law and order are swift to break down, and suddenly we have The Wild West on another planet. Also, it's wise to be wary of Desert Bandits. 

DesertPunk has quite obvious links with Space Western SF!