I'm sure there's many answers, but one would be that it's hard to determine a pedestrian's intent to cross. A vehicle at an intersection, in the right lane - ye

I'm sure there's many answers, but one would be that it's hard to determine a pedestrian's intent to cross. A vehicle at an intersection, in the right lane - yep, you can be fairly sure its intent is to cross. A pedestrian hanging around one end of a zebra crossing can be waiting for a green light, grabbing a smoke, chatting to a friend or playing Pokémon Go for all you know. There's no good way of automatically knowing that they intend to cross.