Look more carefully at that 50 to 70% figure. It is exaggerated (or at least misleading to directly compare) because the usually cited studies are assuming an arrest with a shockable rhythm (and timely, and correct AED application), but only 30 to 40% of out of hospital cardiac arrests have a shockable rhythm, so the overall survivability is not over 50%. Practically speaking even with an AED present its more like 20-30% and that is just survivability, not taking into account long term deficits.
They're cheap enough now for normal people to own one.
I carry one in my car as well as a bleed kit, and some other bits and pieces I'm qualified to use (oropharyngeal airways and a bag valve mask respirator).