"Developer time."
I'm wondering, exactly how much time do you think creating this mode would possibly consume?
Maybe a single day?
I think it would be worth it as many console players would be, as you've said yourself, missing out.
Having played around with the CS a bit... It probably wouldn't take more than a few days to code, playtest, evaluate, calibrate, and integrate. The trouble comes when tweaking settings across the default game... the playtesting process for hardcoe mode needs to be retested after every major change and in every new version of the game, and further played with to truly work. It wouldn't be too hard... but might be more of a waste of time than simply including the default enemy HP/damage slider that only needs to be coded once.
Then comes the world design choices that need to be made to guarantee the player a place to sleep often enough to not incur penalties, enough readily available food, etc...
Plus, can you imagine fighting an epic day long battle with a dragon... only to collapse from lack of sleep?
EDIT: As mentioned earlier, I won't likely be using a hard core mode feature, even if it was included. I'll be playing Skyrim on Xbox 360 for probably a year before I can afford a decent gaming rig. Oblivion already taxes my laptop's resources on Medium settings. I fully realize that I don't speak for every console player here, but I don't honestly see hard core mode as being worth the hit to developer time it take to do it right.
As mentioned by others, I feel that Bethesda's wonderful modding community will produce dozens of hardcoe mode mods that will blow any official mode out of the water.