However speaking as one who has been known to tailgate (must be a minority of 1 in the world
) (actually I prefer acute aggressive driving syndrome to the distasteful descriptor of tailgate) When you are in traffic and the person in front of you refuses to allow you to pass even though you have flashed your headlights or even blown the horn. Changing their mind by acting on ones sense of self preservation (be it life or monetary) can often accomplish what courtesy or a naked threat will not.