Because that's a "switched" power source. Look people, stop telling me to return it...IT WAS FREE!!!!!! If you do not know how to hardwire this or make the harness, don't post anything.
Wait!
No need to get pissed because someone is telling you to do it the
RIGHT way.
When butchering electrical work, there's bound to be a problem down the line
Without seeing what you're working with, here's what you do
Install the bulbs into the aftermarket headlights
The two wires from the bulb must be connected to the Ballast
The factory headlight connector (where you plug the stock bulb into) must be connected to the other side of the ballast
Basically, that's for a simple plug-n-play
But it would help if you posted some pics so we can know what you're working with and if you're missing anything
As far as hardwiring stuff, it's basically simple.
Just figure out which is positive and which is negative.
There is no need to wire anything to the parking lights as the headlight connector is your power source