The way I understand it is that CPR is for a dead person.
You’re resuscitating via the heart and lungs which aren’t working. The chances of pulling someone back from the brink are very slim unless you’re there at the exact moment the person needs it.
You’re just helping to push oxygen and oxygenated blood to the organs to keep them alive for a few more moments before the emergency crew gets there to take over.
I’ve personally performed CPR in and out of the hospital setting at least a few hundred times and have only seen it work twice to where the patient was stabilized and not needing CPR anymore.