Robocars - Autonomous Drive, Self-driving, Driver-less cars

Ultimately the conversations between a doctor and a cancer patient are founded on lies to make a patient feel better.
Perhaps there's a more nuanced explanation - Communication between doctor and patient goes through expression, filtering and interpretation.

Add to that the psychological stresses of potentially fatal disease, with all of the denial, bargaining, and so on, and the path that the patient chooses, while rational, may not follow the rational path of a third party, or in the example of the doctor with the cancer, a first party.

So not lies, as such - just a different reading of the truth.