Because the original parent comment is using an analogy to aviation terms, and depending on a more than cursory understanding of the limits of an aircraft autopilot. I am willing to make a monetary bet most members of the population do not understand the precise limitations of an aircraft autopilot, though I admit I have not conducted a poll to verify this. I also think Tesla likely named it this to differentiate it from the competitions systems, and in my eyes it is pretty obvious what distinction they were aiming for most people to make.