A lot of characters are marked essential, until their no longer needed for a quest. Why is it, at the end of The main story can you not kill Delphine. You are forcibly given the quest But why not her? If you choose to go your own way, and not join Then fair is fair...I realise that since this time there are mods to kill her. That doesn't help us consol players...Just wondering if anyone has come up with a reason why she was not made an option, like many other essential(until) npcs.

BECAUSE, they don't want players to kill an important NPC and then come back and byatch about it, how they "broke" the game and can't do quests because of it.
"OMG i wanna play the new dlc but i killed that dude for no reason at all a long time ago, WHY WON'T YOU LET ME PLAY MY GAME ON THAT CHARACTER? BETHESDA YOU svck!!!"

They could have just made it so a note saying "you dun' goofed" showed up when you did kill one of them instead of making them immortals.
Like Morrowind!

Well thanks for such an eloquently put responce. Too bad its useless.
Show me where, in what dlc she is used again?

None. She just never loses her essential status.

Ah, the wonders of the quest of killing the "bad dragon" for delphine. I suppose I can remove her essential status this time.

She can boss around someone else in sovngarde.

Not Delphine specifically, just in general, where you able to kill that boatman that takes you to solsthiem, how could you possibly play Dragonborn? People are going to complain either way, so Bethesda might as well play it safe than sorry.

You never know if a current NPC will be needed in the future. If the NPC is an important character, odds are they don't want her to be killed and then end up having her as part of a DLC.

Like the woman that takes over the Honorhall Orphanage. Not sure if she is essential.

You n'wah, I was talking in general. Not just about Delphine.