Hood insulation, keEp? Remove?

I have noticed that a LOT of the cars that have the insulation panel removed from the under side of the hood. Is that done just for looks, or is there another reason? I am making plans to detail the area under the hood, and am thinking about removing the insulation before I paint. also wanting to install the 340 hood scoops, prolly need to remove it anyway? Any problems with removing it? What is it even there for?!