I think pretty much everyone would rather die than linger on in a hospital bed without hope. At a certain point, utility of future life becomes negative and returning to a positive state is not possible. The problem is that it's not so clear cut and obvious at the time that this is the case. A big part of this is that doctors often want to save the patient at all costs, and often deceive themselves as to the patient's prospects. So often even the patient has no idea how bad the situation is.