Well I know when I first bought my AR, before I upgraded to the quad rail...I went out on a hunt that was about 40* and raining. I had on leather construction gloves from walmart i think. My hands have never been so cold in my life. I was actually hoping that I wouldn't have to touch the tube because it transferred the cold so easily.
Since getting the quad rail, and getting 2 different kinds of rail covers (I prefer low pro ladder rail covers) I've never had my hands get cold. Your hands stay elevated just enough that you're not in 100% contact with the bare metal. Not only that, but you'll find those rails are SHARP when they are new.
They protect your rails that arn't being used from dings, they protect YOU FROM THE RAILS and they can give you a better or more familiar grip on your rifle.
Are they necessary? You'll have to go without them to find out, but I'll be putting them on any quad rail I ever get.
