When installing aftermarket head units, you will be required to make the connection between the OE harness from the vehicle to the aftermarket leads on the stereo. Usually, you will need to cut the original harness on your car in order to do the wiring to the stereo. However, with the harness adapter, you are able to wire up the stereo and just plug in to the vehicle side harness without cutting the original harness.
Avoid cutting the original harness on the car
Able to reverse the whole process and reconnect the original stereo
Able to keep your aftermarket stereo with you should you sell the car
Not jeopardize radio reception
Have a cleaner install overall