Traffic flows in stop-and-go waves that are caused, in part, by everyone doing their best to prevent other cars from cutting ahead of them in their lane.
By not tailgating, by giving lots of space to the guy ahead of your car, you allow cars to flow into lanes as they want. While this may put you a few cars back in the lane (temporarily), it also reduces the jams that would have been caused by those cars were they not allowed to switch lanes. See video for more explanation.
This change in perspective will calm you during your commute and, perhaps, get you to work or home a little faster during rush hour.