Does a lot of things that add to the immersion that they'll be too afraid to ever do again for the sake of convenience. Faction quests that will ruin your standing with another faction, so you can't complete everything in a single playthrough (you'll still have plenty to do though, and it leaves more for future playthroughs). Fast travel costs gold and only exists in ways that make sense in-universe, you'll have to walk to anywhere else you want to go like a cave and NPCs will usually give detailed instructions on how to get there without quest markers. You can kill anyone, even NPCs essential to quests, and you may want to do so because of an item they have or because it's the way you're roleplaying your character. You can fly anywhere, and there isn't any spot you could get to that'll break the immersion like the walled cities in oblivon and skyrim being interior cells. Dungeons with optional paths and secrets, some requiring levitation.