Imagine that you are an object in motion - you're moving; you're traversing the surface of the earth in a forward direction. Now imagine that you are not only not aware that you're moving, but you're doing so by your own hand - everything surrounding you was accomplished by your direct, purposeful action. Yet inexplicably, you are unaware of how you got there, or what is supposed to happen next. Perhaps music is playing or you are deep in thought, or communicating with someone close to you.
Now I ask, is it really considered tailgating when the person in front of you isn't even aware they're behind the wheel of a car? I consider it an expectation that at any moment the person in front of me will wake from their alternate-reality dreamlike state and at least attempt something close to the posted speed limit.