It's not uncommon after a severe head injury such as in a vehicle crash. Some of these patients, if kept on a ventilator and other support, may not meet the technical definition of brain death for a long time, and quite possibly not until organs have deteriorated to the point where they're unuseable for transplant. But their brain injuries may be so severe that there's no realistic chance of ever regaining awareness. If they also have physical injuries that would kill them soon anyway, and likely require them to be kept in a medically induced coma or heavily sedated in the meantime, what's the point? Most people would WANT to save other lives, if there was nothing else they could possibly accomplish in their short remaining life. Of course, people should be able to opt of being donors at all, but if you want your organs to go to others when you can no longer use them, the law shouldn't prevent that by imposing requirements that will often prevent the dying person from donating organs that will save others.
>> a patient who has been languishing in a hospital bed on a ventilator, showing no signs of awareness, and lots of signs of severe and permanent brain damage.
The picture you painted here is pretty much a dead body. The damage is "permanent," the patient is languid, comatose and presumably brain dead (ventilator). There is no hint of hope. The patient is being kept breathing for no reason. I wondered why? It doesn't ring true. Hospitals as a rule don't waste thousands of dollars a day on futile care.