I think enough of the population has become convinced that dog in car = OMG DEATH!!!! even in climates where that is not true year-round, and enough states have passed laws allowing owners to be fined, that people call 911 and cops come even in cases were there's likely no danger to the dogs.<quoted text> Someone leaving their dog inside the car on cold day is not going to incur the wrath of Johhny Law unless its so cold that it could harm the dog.
I know that the growing opinion against leaving dogs in cars has changed our opinion, for example, regarding taking the dog on vacation with us. Even if we're camping, it's hard. Easier just to board the dog. 15 years ago, we took the GSD we had then all over the the US with us. He got left in the car when we judged it safe enough (we were generally travelling in the spring or fall). This past winter when drove the current dog from Illinois to Washington, she was never left in the car alone. Even though the car would have stayed warm enough for us to go into a restaurant for an hour and leave her, it wasn't worth the risk of someone calling the cops on us.
We ate three days worth of fast food. I really don't ever want to do that again.