If you park in a driveway or in someone's yard where the leaves are not raked (in the fall), the lower portion of the heat shield will protect the car from catching the leaves on fire.

Back in the day in high school when I had my first car, I pulled into a friend's driveway and he hadn't raked all the leaves. He was a lazy ass and made me pull all the way up to his house through the leaves. A bunch of them got jammed under the car and caught fire, I had to grab a rake out of the hands of the old lady next door to get the damned leaves out from under my car before they roasted the thing. Car smelled like a brushfire for about a month afterward.