LOL at Best Buy being "high end".

some cars have a 4 wire connector because the NSS is also the switch for the back-up lights. To find the wires for the NSS you just put the car in park and see which two wires have continuity with a multi-meter.

I guess one would want to by-pass the NSS as a test to see if the NSS is bad or not. Or if you're swapping from auto to 5 speed. Those are the only reasons I can think of.