I think it was a safety thing. For whatever reason I you needed to cut the power to it you could. I didn't install the system I just put switches in a different location. If the car is gonna sit for a couple days I usually just cut the power to the amp as a "just in case" it decides to drain the battery. And the ambient lighting on/off is so that you don't have to go to the 12V power point.
I dunno, it's just more of a OEM look that I might go to sown the road.
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2003 SVT focus
Build number: 61 of 3985