On one hand, this made the RPG feel more immersive. In Morrowind, every character was capable of dying, regardless of whether or not it rendered the main questline incompletable.
Skyrim takes a different approach to story-important NPCs than Morrowind did. These characters are marked as essential for one reason or another, usually due to their involvement in important quests during Skyrim's primary storylines, and consequently might be more helpful to have around, especially at higher levels. Of the various followers that can be found throughout Skyrim, only a small number of them are incapable of dying.
