Keeping your eye on the road matters. Sometimes it just prevents you from being a jerk, other times it can save somebody’s life.
Case in point: Earlier this past week I was going down Oak Street looking for a parking space on the street. When I saw one, I immediately hand signaled (my car is 63 years old and lacks turn signals) and slowed next to the spot. A white SUV was approaching behind me from the intersection, so I held the hand-signal for a few seconds, believing that the SUV would see the signal and leave me sufficient space.