[MargaretR]

We need to keep prisoners healthy so that when they come out they wont be spreading disease among the law abiding population, and be fit to work, so do not continue to draw off the state for their keep. Vermin go hand in hand with many diseases.
The original principal of having a free for all health service was so that infectious/contagous diseases would not be spread amongst the whole population by sick persons who had no money to pay for treatment.