Yet another prime example of an old time habit that won't die.
Sure, if you have just parked your semi hauling 50,000 lbs across the mountains, that engine has been working very hard and a cool down period is advisable. Likewise if you have just plowed 50 acres with your Steiger. Likewise if you have just pitted from going 180mph in a Le Mans race. But just in from puttering around on the street? I don't think so.