I'm pretty sure that in "socialized medicine" countries i.e. the rest of the civilized world pretty much, they also "do everything" even if chances are low. AND everyone involved (including family) can do their part in it without having to deal with papers, money, bills, proof of insurance, and the plethora of other likely speed bumps that exist in the US.

So no, I don't think that's why. If anything, the amount and quality of average care for the average US citizen is lower, if life expectancy and my anecdotal observation are valid indicators.

It's expensive because it's a business designed to make profit every step of the way, and over time has created many steps to feed.

I'm no expert but at least in the initial stages of resuscitation, the cost is relatively low. Paramedics doing CPR, defibrillation, some epinephrine, then in the ER they'll intubate, get some lines in, push more epi and maybe amiodarone - pretty basic stuff that's more about doing it fast than expensive equipment. I don't think it adds up to a ton… well yes American healthcare is absurdly expensive, but this particular aspect isn't extraordinary. The initial resuscitation steps are about timing, not fancy drugs

Even if they die, reviving them still opens the door for organ and tissue donation.

IMO it's still good that it's family's decision. Even if it is an incorrect one.

The biggest reason is probably that you need to fit a medical insurance agent, a lawyer and a doctor all around the same hospital bed to give care.