Earlier quoted context omitted.
If the father became unconscious, had a stroke or a heart attack, etc. while driving or doing anything with the child away from other people, the child could die.
Yes, driving to the store is considerably more dangerous for the child (even if it's in correctly fitted car seat (and many children are not)) than being left for a few minutes in the car. Still, leaving the child alone leaves them open to more risk than taking them out of the car. This parent was not buying anything important - just headphones for a child - and they took the wasy options by i) taking child to shops…
So a child in an immobile tested-safe metal box with ventilation, locked and alarmed, is more at risk than being outside the car? I'd like to understand how you came to that reasoning.