sanquin said:
Those are not key npc's. Key npc's are for the main quest, for instance. And you can't kill such npc's in Skyrim. Take the companions dungeon quest. You can't kill the one that's accompanying you. Take the Greybeards, you can't kill them either. In Morrowind you could, and if you did you'd get a message box with a roleplay message that your quest had failed (even the main quest) and an option to continue playing or start from a previous save again.
You are aware that the only reason you could do that in Morrowind was because NPCs in Morrowind stayed rooted to the spot they were in for all hours of the day, and ever never in any danger of dyeing by anyone's hands but your own?
However, with the advancement of dynamic NPC schedules, such as them going to hunt for food, or them going to market to buy food, or them going to check on how their farms are doing, and with more dynamic world interacts like Vampire/Dragon raids, NPCs CAN die by hand other then your own, which is why they are unkillable.
And given how much people HATED how many NPCs were dying because of random vampire raids on cities for the Dawnguard DLC, the simple fact of the matter is, most people dont want it in a world where NPCs do something more then just stand in their houses all day.
Not to mention, how many times in Morrowind did you actually just randomly kill a MQ giver? or a important NPC from a guild? In my case, it was NEVER, and I have never heard a case of it happening outside of instances were people just deiced to go on murderous rampages for no reason beyond to just try an kill everyone, which the vast majority of people never did.
Being able to kill everyone meant nothing because almost no one ever tried to kill people who weren't already hostile. the only real reason I have ever seen people complain about it being removed is for the simple fact that it was removed, and not because they actually used it.
They changed it not it sucks comes to mind - http://tvtropes.org/pmwiki/pmwiki.php/Main/TheyChangedItNowItSucks