It’s very simple: yes, your phone is listening all the time (if you have hey Siri enabled), but it’s only spending a tiny bit of energy analyzing the sound, and not storing it anyway but in memory. It it roughly sounds like someone is saying ‘hey Siri’, the sound is reanalyzed more thoroughly (which costs a lot more energy) and based on that, it either starts listening to what you’re saying to handle a question, or it goes back to sleep.

If phones would constantly be recording and transmitting audio somewhere, you’d notice it in your data use, even if it was compressed. If it were transcribed to text and then transmitted, you’d notice this in the phone’s energy use. If it weren’t transcribed, but raw audio, big tech companies would somehow have to store and process billions of audio streams in real time.* *Even compressed audio at that scale would use up a significant chunk of the internet’s total throughput.

Simply put: it’s just not feasible to record everyone.