Even the most skilled drivers cannot out-smart a stop sign.
Scenario 1
You pull up to a stop sign for a right turn and see cars off in a distance. Why stop? Only when you stop can you take time to properly judge how fast cars are coming at you. You can also see if there are people (or other factors, like other people going through their stop sign) preventing you from moving forward.
Scenario 2
You pull up to a stop sign for a right turn and don’t see any cars at all. Why stop? Only when you stop can you properly look around to see cars, people, bikers, animals, etc.