Clear back glass replacement antenna questions

Okay, so I just received my clear back glass replacement for my iPhone 4S. I know that there's an antenna pressure connector that makes contact with some of the metal on the stock back plate. There's no metal on the new backplate. So my question is, why is it that all of my phone's wireless freq's seem to be working great (WiFi, Bluetooth, AT&T 3G/(fo 4G) cellular, etc). Are there specific types of cellular signal that use this antenna? It seems to me that it's not necessary.