Some people find it an abomination. Others get tears in their eyes when they see the beauty of a manifold or exhaust system wrapped in insulating tape.
But it is useful. The gas flow from the block improves, and the temperature under the hood can fall considerably (sometimes up to 50%).
And cold air gives a better mixture, better combustion and more power. And that the indiep black, warm red, yellow or white is available?
And for motorcycles with ugly exhaust bends, it is a tough and cheaper alternative than new exhaust bends.