I wonder how old is old enough to be left in the car while a parent runs into the store? I'm not talking on a super hot day (though, with an older kid, the car could be on with A/C running and the doors locked). I know it depends on the kid, the town, etc., but, I was thinking about it, b/c people let kids walk home from school alone, or walk to a friend's house alone, or stay home alone, or stand outside a store or bathroom alone. So, there has to be a point, before like age 16, where it's acceptable to leave a kid in a car and run in for an errand.
IMO- it varies. I am comfortable with it for a SUPER short errand within sight with my oldest (almost 10.)
Once I would be comfortable with them getting through the parking lot alone, or being at that store alone, I suppose? I won't leave mine outside of a large shopping area (Target/Walmart) but would outside of our local grocery store and MIGHT if the littles fell asleep and I realized I forgot xyz when I got groceries. I'd stop at the smallest store in the larger own, but I might be out of sight for 5 minutes or less. I'd probably try to avoid that, but if the weather was ok and I was in a pinch- sure. In another couple years when DD has her cell phone I'd be fine with it.