Lot of people get CPR when in reality they’re dehydrated, ODing, or something similar
If you don't have Narcan on hand, and they're not breathing, rescue breathing might keep them alive until the EMTs come. If they don't have a heartbeat, chest compressions might keep them alive until the EMTs come. CPR's rate of success isn't great in most circumstances, but it's much better than nothing. No pulse, no breathing, their chance of death by the time EMTs arrive is essentially 100% without CPR.
Care to cite any examples in the US of prosecutions or civil cases that weren't immediately tossed within the last 30 years? This was once a problem. Good Samaritan Laws were passed to fix it, probably before you were even born. You're just making stuff up.