If it's inconvenient to you then you always have the option of checking out of the hospital whenever you want: you are always (except in psychiatric hold cases) able to sign a form saying you understand it may be Against Medical Advice and want to leave.
There are other ways; they are more expensive, less accurate, and possibly more dangerous to the patient, but they exist.
But if you go back and read my comment again, you'll see that I'm talking about the popular belief that losing consciousness is detrimental to the patient. It isn't; it is beneficial. The doctor may have good reason to keep the patient awake anyway, because, if the patient suddenly starts to die, he might be able to do something about it.
But if you are not in that situation -- if there's nothing you can do if your injured friend suddenly starts to die -- then you should not be trying to keep your friend awake.
Actually, speaking of practices that are implemented for the convenience of administrators rather than the benefit of the patient...
There is a popular belief that, if you have a head injury, you must stay awake because losing consciousness is dangerous. This is completely false. Your urge to sleep reflects the fact that that is what's healthiest for you. If (1) you are caring for someone with a head injury, (2) they want to sleep, and (3) you have no means of addressing a very serious problem such as massive internal bleeding, you should let them sleep, because that is their best chance to recover.
It is, however, absolutely true that, if you have a head injury, 911 will tell whoever is caring for you to make sure that you remain conscious, and if you're already in a hospital, the staff will do their best to ensure you remain conscious. This is not because staying conscious is good for you. It is because they are relying on an index of how severe your injury is ("is he behaving oddly?") which only applies if you're conscious. Everyone who's unconscious is behaving normally.