my father has a deer guard on the front of his truck. home built from T1 tubing. (the stuff they make cranes out of). it weights about 120#, pins to his plow bracket.
not the prettiest looking thing, however it protects the radiator and head lights.
he did it because he must have hit at least 30 deer and about a dozen large birds (pheasant, turkey, etc) over a 20 year period between his truck, van, etc. he hit 3 in one night on a back road to a camp site and a few years later, took out 3 in one day with 3 different vehicles. usually during rut. the one time he completely stops for a herd of deer crossing the road, two run into the side of his van busting out the passenger window and smashing in the sliding door
there is a reason there are a lot of body shops in northern wisconsin and the UP
the purchased "brush guards" weight maybe 30# are made of light-weight thin-walled tubing, and as fhhuber pointed out are decoration