You don't want to live half your life as an over-60 geriatric, with daily pains, vocational ostracisation, inadequate income, and decreasing social relevance?

Mind you, some would bin that in with the douchey "I wouldn't want to live if I became paraplegic/deaf/blind," but I do fear that, given how crappy it is to be 75 today, it's not going to be senior Disneyland by the time I'm old. Older.

Put my brain in a jar and I might have a different perspective, but I've seen enough family members admit they're just tired and want to go when their time comes.