Everyone being liars means you and I are both liars, same as the politicians. But the politicians have the power and if we remove two party consent then they get to surreptitiously record you and leverage that power. It doesnt even the power playing field.

We can alreay write notes down for every conversation and then send them to the person involved saying "we talked about X, Y, and Z." That last step is the key because it lets them object in writing if you mischaracterize things. From a "catching someone in a lie" the most important step is that one, because you form a paper trail where the other party can correct or contest what was written and bring that up now, and the fact that they didn't is itself evidence in case of a dispute later. The apple watch feature doesn't do that, it just dragnets everything. Even if it recorded the audio, we are in a faked-audio world so unless you have some signal that they agreed that they said a thing ahead of time, they can always deny it later.