"Sounds like you would be constantly be speeding up or slowing down or changing lanes." Isn't this always the case in the city? I have never been able to set my cruise and never change speeds or lanes while in the city. If you hold your speed "because the book tells you you can" aren't you one of the self centered people?
Drive defensively, adjust your speed and change lanes as needed for the scenario for those that are merging and for you when you are merging. "The rule book" is a guideline, not a hard, never to deviate, carved in cement driving technique.