Another aspect of the backstory in making the PT is that of all the planets in that galaxy far, far away that we were yet to see, Lucas chose Tatooine, a planet that already overstayed its welcome in ROTJ. You could easily fan edit ROTJ to make Jabba's palace and the Pit of Carkoon on some other planet, It's not like they shot it in Tunisia anyway. Because of the choices Lucas made, the same could not quite be done for Tatooine in the PT. I could make a couple guesses at why he did this. One is for the convenience of Owen and Beru's backstories. The other is that maybe he just couldn't think up another planet that was different enough of an environment to justify not making it Tatooine. You've probably all seen those lists that people make. Bespin is clouds, Yavin is jungle, Hoth is ice, Dagobah is swamp, Endor is forest, etc.