Because there is no sharp line, where to draw the line depends on context, and the point being made. I have found that "AI" is a good term to apply when it is more useful to take the intentional stance[+] to explain an artificial system's behavior than to trace the actual low-level implementation.
At the very lowest end I could include some closed-loop control as AI (a simple proportional controller wouldn't count, a PID might). The more complex the model it has of the environment, and it's own effect on the environment, the more useful it is to call it an AI.
A slightly more complex example are computer games, whose simple AIs are generally readily explainable from their code. In an RTS game with good AI, it's not useful to look at how computer opponents (or my own units) do pathing, only where they're trying to go, and the obstacles they'll encounter.
ABS is lower than I would normally consider AI to be a useful descriptor because of how little information processing occurs (basically just wheel speed and brake pedal trajectory). In this context it's worth not excluding precisely to emphasize that AI is not just machine learning, but just about anything that autonomously makes intelligent decisions in response to changing environments.