This, of course, is not only an American phenomenon. It is rather a necessary evil of the big city dweller.
People have to be in constant motion in order to prove that they are doing something.
The thought of sitting somewhere, contemplating, meditating or just observing things is as foreign to laptop carriers as laptops are to fishermen on the Amazon river. It would be safe to say that these men don't appear to be very happy, to say the least. I used to number myself among them, but now I have been redeemed. I am free from parking lot rage. I found something worthwhile to do while waiting.