There are a lot of non-sensical things in the bike world. I blame it on fashion and being "cool". For instance, who wouldn't like to have a Ti derailleur guard over the RD? It might save your hide one day. But alas, I've only seen them on kids bikes. I for one, like a chain ring guard. I keeps me from getting long pants dirty, getting chewed up in a fall off the bike, or damaged if you hit a rock.