Because only a small fraction of cars have them. Jay-walking can be dangerous. When you know that all cars will stop for you, it becomes a lot safer to just c

Because only a small fraction of cars have them. Jay-walking can be dangerous. When you know that all cars will stop for you, it becomes a lot safer to just cross the street wherever you want. http://en.wikipedia.org/wiki/Risk_compensation http://en.wikipedia.org/wiki/Risk_compensation