Each location in Oblivion and Skyrim was hand placed by the developers when the game was created. Arena and Daggerfall used a completely different game engine that is not compatible with the way Oblivion and Skyrim were made. Playing Arena if you uninstalled and reinstalled the game, many dungeons and towns would be in a different place ( procedurally generated psudo-random location) While every time you reinstall Skyrim and for everyone that plays it every location will always be in the same place.