Two reasons I can think of immediately for a brush guard beyond "looks":
For me (and most people I know), a brush guard services the purpose of deflecting downward or away small undergrowth (tall weeds/grass & small bushes) to protect your vehicle's paint, headlights, and any other components you've mounted. Even tree branches have a habit of "smacking" into your vehicle and cracking or breaking things.
For most people that strictly use their vehicles on streets, highways, and well maintained roads, there still is the issue of deer, elk, and other animals crossing in front of you. While 35-40 MPH doesn't seem like much, these bodies have a way of damaging or destroying your vehicles front end. Front mounted "deflector" systems can also keep the large object from coming over your hood and smashing into (or thru) your windshield). At the least, it can protect your radiator from being cracked or punctured. While you will not get away without some damage either way, at least you are not stranded with a vehicle that cannot operate.
Just my thoughts...
"Life is hard. It's harder when your stupid. I'm hoping I'm only ignorant..."
Last edited by SpentRound; 01-09-2013 at 09:35 AM.