grounded rca

I ripped apart my interior to add rear speakers and I noticed my front door speakrs that are hooked to an amp are grounded, as in someone slid a piece of wire between the wire and th rca plug on the back of hte deck and stuck them together, then grounded the wire. Why is that, what if i pull it out, I don't get why that was done.

Tahnks for the response, it's actually a , forgive me if I miss a number, pioneer premier deh-960mp or something like that, it folds down to reveal a pretty screen. Assuming it doesn't have the pro standard thing, would it be ok to.. hook the front speakers to the FRONT rcas, wire my rear speakres to the rear wires on the wiring harness..then..idunno about the tweeters. Woudl those go in line with my front speakers that are hooked to the amp?

Whoop sthat post was supposed to go in another topic, but yeah it's a pioneer radio.

Did you try ungrounding the wire and test for lots of engine noise?