My husband loves to take the dog with him on errands and will leave him in the car when he runs into Home Depot or something. It’s not usually a long time but I hate when he does this. I think it’s probably anxiety producing for the dog to see the owner leave - and then see all the people/car activity around them. At least our dog might have anxiety over this!
I also worry about the dog getting into something in the car that he shouldn’t or barking or even someone managing to steal him!!! H and I have had lots of disagreements over this!