Boy on Top

Why is it that people are only polite to that which is in front of them? I mean, if you're in a long queue of cars, often the car in front will politely let a car in from the side, even though that car hasn't queued. This is illogical. Stopping to let the other car in actually worsens the queue, plus the other car has not "paid" in time the way those in the main queue have. Yet people see the car, and think they are being good and virtuous by letting it in, when they're not. The same in crowds, people will maneuver and stop to be kind to those they see, with no thought to those they don't behind them.

Am I being mad here? Is it incontrvertible human nature to only be considerate for that which you see?