True, but you also might not have time to react and hit the brakes if someone darts out in front of you.

Unless you were texting while driving, changing a song, eating, talking with a passenger, or talking on the phone (even handsfree).

Or, it was dark, your (night) vision isn't the best - but passes the drivers test, or you were tired.

You might also rest your foot on the brake in anticipation. But neither attention nor anticipating controls is a concept that really exists in these autonomous system. They're "always ready". (yeah "attention" can exist in perception neural networks, but I am not sure that has much to do with keeping an eye out for a risky event)