Why artificial intelligence must disclose that it's AI

Google recently repitched Duplex to explicitly reveal to restaurant hosts and salon staff that they are speaking with the Google Assistant and are being recorded. Google omitted this small but important detail when it first introduced Duplex at its I/O developer conference in May. A media backlash ensued, and critics renewed old fears about the implications of unleashing AI agents that can impersonate the behavior of humans in indistinguishable ways. By tweaking Duplex, Google puts to rest some of that criticism. But why is it so important that companies be transparent about the identity of their AI agents?