Because AI Focus is more frequently wrong than closing your eyes and guessing whether the subject is moving or not.

Yeah, but at least you have all the control at one button. You can always just keep bumping it. It will still work faster than you can when working between two buttons. Besides, AI Focus is basically all he wants, only to work it manually between two buttons instead of relying on it to work automatically.
May as well just leave it on AI Servo, which is what I do now.

