To control noise.
Direct exhaust fumes away from the passengers.
Enhance the performance of the engine.
Improve fuel consumption.
Corrosion of the exhaust can happen to the inside and outside of the piping. The lifespan of your exhaust will depend on the frequency of using your car and the length of journeys. If the silencer is damaged in any way, you will be able to hear the result and will need to get it replaced as soon as possible. There are a few hints that might suggest a problem with your exhaust;