I think you're still missing the point. It's not that talking on the phone or using a GUI is more efficient, it's that it allows people to use technology in a w

I think you're still missing the point. It's not that talking on the phone or using a GUI is more efficient, it's that it allows people to use technology in a way that feels more natural to them, and requires much less training to be able to utilize it. To your point about clicking vs knowing commands, a GUI is more discoverable for someone, because they can try things and see what happens. Trying to guess commands is much harder, because there are no clues to guide you.