Serious question: if this is the case, why does my phone's battery last significantly longer when sitting idle and not making calls vs. when I'm talking to peop

Serious question: if this is the case, why does my phone's battery last significantly longer when sitting idle and not making calls vs. when I'm talking to people on it? Surely the energy cost of constantly transmitting audio would make the battery drain very quickly. Then there's the issue with the towers/lines being jammed by every phone constantly transmitting.