We had two Hallmark Stores in my town growing up and they were constantly doing giveaways like this around the holiday. It seems silly that a plastic bag would bring in people to a store, but it worked. My Mother and Grandmother would wait until they were sure these were available before buying Halloween cards to send to cousins. They did a similar thing at Xmas time.
I am not sure we ever actually used these bags for Halloween. I had a pillow case and a plastic pumpkin I liked to haul around, but we would instead use them as disposable tote bags when we went to the shore in the summer. That’s right, we were the family trying to find a spot on the sand carrying our Frisbee and snacks in a Halloween and Xmas themed bag.