The reason exhausts are loud is that there is detonation happening inside the exhaust. This happens when you increase the fuel-air mixture above what the cylinders will support for combustion and often gives slightly (maybe 10%) better performance of the car, for the cost of much lower lifetime of many components (not just the cylinders), and of course making enough noise to wake the dead.
There's plenty of motorcyclists who do the same though.
There's plenty of motorcyclists who do the same though.