[jimmy1]

And also to not incite road rage from their fellow drivers because they are sitting stopped at a green light. You could also cause a fender bender because other drivers, who also may be distracted slightly, are expecting the cars to move and then are startled when they look away for a brief second because the car in front of them had to brake for the car stopped at a green light. Some states hand out tickets for being braked at a green light.