I think most parents get their kids in the car first because kids hanging around in the parking lot with cars pulling in and out is hazardous and kids can be dumb. Hard to keep an eye on them while you’re unloading things so you put them in first. Then of course if it’s warm out the car is hot and kids will be complaining so the parent starts the car to get the AC going while they secure the kids and then unload the groceries. Once done of course they have to decide… walk away from the running car with your kids inside and put the cart away, or not. I can understand why sometimes they dont.