It’s there so that when Grandpa Steve does 15 lines of coke and smokes a full bong of premium weed and passes out he’s not taken to ER to take a spot from someone who needs it.
I guessed that but I doubt Grandpa Steve cluttering ER for a couple of hours from his coke overdoses would be a significant issue compared with his being at the hospital for several years with alzheimer's.
BUT to get immunity from prosecution they'd have to sign a notarised and confirmed Do Not Resuscitate order.
Call it the Blaze of Glory act or something =)