It knows what you rolled
The one thing a microphone cannot tell you
Most session tools listen and summarize. Six Axes also captures the mechanics: attacks, saves, damage, hit points, who rolled what and when.
That lets it do arithmetic nobody else can. It knows the fight it called Moderate left the party at a third of their hit points, and it can tell you your Moderate encounters land like Hard ones, at your table, across a whole campaign.