Exactly. And the conspiracy theorist in me thinks it is quite likely that the phone's microphone is always on and listening, and that anything said anywhere near the phone is also recorded and stored in that massive NSA data center outside of Salt Lake City. The 4th Amendment, like most of the others in the Bill of Rights, is violated with impunity by our government.
If you watched any of the documentary about the Murdaugh murders in South Carolina, you got a good look at just how much data from your phone they can access. Right down to what app you were looking at at a specific time, whether your screen was locked or not, etc.
The battery depletion rate for that would be obvious to you. If you use a radio spectrum analyzer tuned to cell tower frequencies, you would see tower check-in messages every few seconds. The check-in messages keep your phone's position known to the network so that call routing can occur without the need to do a global ping. When you have a conversation going you will see short messages originating every 20ms, and received at the same rate. Video upload will occur at the same rate, but the messages will be a lot longer.
The cell phone's transmitter musters about five watts to a distant tower. That blows through batteries pretty fast.
You would also notice your local storage filling up pretty fast if they were recording your conversations for a fast uplink when the phone is connected.
Since they intercept ALL of your voice, text, data, and video streams, there isn't really any need to listen to your in person conversations. If you watch people, they don't usually converse with people whom they are with. Everybody conducts life through the cellular network.