I don't shop at walmart. I also don't have unreasonable expectations about ppf. It's not a force field.
edit: less snarky response is that ppf won't stop blunt damage from a large edge of a car door if someone smashes your car with it. The odds of being hit by a car door is significantly less than rock chips from driving around thousands of miles behind other vehicles. My last 5 cars have had front ppf, and I never had damage on the sides of my vehicles. But I also don't park up front or shop that often.
LOL His damage didn't happen at Walmart (not sure where that came from), in fact one location was an upscale grocery store and he doesn't park up front but usually further away from most of the traffic. While you haven't noticed door dings and such on your car I think it's important for the OP to consider stuff like that happens often enough as well. Plenty of people to attest to it. Most people go shopping or dining and park in lots or garages - albeit not so much probably with covid these days. I do think if you are only going to do a limited PPF the front of the car would be priority.