My theory: No, they are not for looks! In '08 they increased the size (or density) of the Catalytic converters, therefore increasing the heat from the engine. Those covers are to help keep the heat off the legs!
My 2010 and 2012 produce more heat down by the front of the mufflers (where the Cats are), compared to the other bikes, '04s and '05 I have ridden. I also notice more heat up near the gastank, and the gas gets much hotter. Just ask my boys. The two pre '07 bikes ('04 & '05) ran much cooler than did the 2010 when we did our SorthWest Tour back in 2014.