I try to do that. In some areas if you drop back to let them in, you will wind up backing down the interstate and wind up at town in the wrong direction. Seems that if you can get 3 feet away from some of the cars you are lucky.
Too bad that cars do not have some kind of retractable stick the goes out the front and gets longer or shorter the faster you go. Some of the newer cars do have the 'radar' in them to let you follow cars while in cruse control. Maybe the government should make that mandentory that anything over 30 mph it takes effect.