The single habitable planet that we happen to live on is biodiverse, but that's a sample size of one. It is perfectly reasonable for single biome planets to exist, and in fact planetology predicts that they should exist (and at various times in the past Earth itself has been significantly less diverse in terms of biomes). Desert planets, in particular, are almost certainly a thing and may in fact be very common.
The official population figure is 200,000, which is less populous than the average US county. This number is almost certainly too low, and the best workaround is that it refers only to the non-native population and not the total number of Jawas and Sand People but even those numbers are probably single digit millions at best. Huge portions of Tatooine, the majority of the planet even, consist of nothing but empty desert full of sand with no people at all.Originally Posted by Sapphire Guard