The typical first aid kit doesn’t have anything that is likely to save someone’s life—and if it did I’m pretty sure the typical person wouldn’t know what to do with it.
Most car first aid kits have an emergency/space blanket which would very much save someone's life and require no training. Also plastic bags as occlusive bandages, gauze and triangle bandages for bleeding control which require a 1-4 hour class.
Emergency blanket requires no training but people need to know it exists and how well it can solve the problem of being cold. And also yeah you get soaked in your own condensed sweat.
In a car where space and weight aren’t major concerns probably carrying one of those blue tarps is more useful in general. I’ve basically never seen the stuff being listed in a standard first aid kit though. Certainly not the one that came with my car. In winter just want some spare warm clothing too.
Reminds me I need to go through the winter kit I carry.
