You are right that if someone compromises your physical computer and knows your local Mac user account password then encryption won't help.
> How is this affected by wiretap and privacy laws, where you would need the consent of other people in the room?
While the laws differ from state to state, we believe privacy is so important that we recommend users of our product hold themselves accountable to a much higher standard than the bare legal minimum. We believe all users of our product should proactively seek consent from everyone they record even if they are not legally obligated to do so. Not only is this is the safest approach legally, but it is also just the right thing to do.
> At home, I certainly don't want something recording every sound.
We don't record every sound. We prompt you to record audio each time a new Zoom meeting starts. You can choose to record or not to record. You can also pause at any time and delete anything retroactively.