Devs can think that little bit harder and come up with a workaround system. I imagine a team of devs sitting around a table, hitting themselves in the head because they can't comprehend how to work with killing an 'essential NPC' so they all throw their documents in the air, hop up on the table and hunch over, screaming like a bunch of apes.

If they honestly can't find a way around it (it really wouldn't be that hard), then why do it in the first place.

Well breaking side quests is not a problem, let the player deal with the fact they shafted themselves. As for the main quest, easy enough to have the NPCs to be mortal but present a ridiculous challenge to kill or have other NPCs ready to make sure your victory is short lived. Also, you can have multiple NPCs that are essential to the MQ, but only to one part. So if you kill two, you can still have another two that might help you out with that part. If you go through the game killing everything, then yes this breaks down, but in that case - what game did you think you were playing ? Heh.

Personally I would like to see the re-apperance of the Wannamingos in the next DLC or Fallout 4. Those aliens were tougher than a Chuck Norris roundhouse kick...

Lool Well, unless Bethesda want to crap all over canon again, there wont be any more Wanamingos. They're on a generation triggered killswitch, and they were dieing out during the events of Fallout 2. But yes, they were pretty awesome

Oh dear how i miss those damage resistant beast of................. well doom? They was a pain to kill, but that was the fun part

Considering that the next Bethesda game will be TES V, I don't think that would be a good idea.

Older games had no problem doing this, why should this? Developers can think of ways around this and not be lazy by making someone god.

Mostly better animations & dialogues, but without taking anything away from the gameplay. Sometimes I like to think BioWare and Bethesda should merge into something called BethWare and pour the things they are famous for into one, ultimate RPG to end all RPGs. Heh.