I usually have this situation at least a couple of times on every lengthy interstate trip and wanted your thoughts.
I'm in the right lane with cruise control engaged. I'm approaching a vehicle, but not quickly, maybe going 1-3 mph faster. Check the mirror. Another car is coming, maybe going 1-3 mph faster than me in the left lane. It looks like this car will be either next to me or close behind when I'll need to use the left lane to pass. My normal practice is to disengage the cruise control, let the car in the left lane pass, then accelerate, and make my pass. I don't delay the faster car with little inconvenience to me and we both get to go on our merry little way.
What happens on occasion is that the passing car slows down when they get close, preventing my pass and slowing us both down.
My question - is the driver in the left lane being a jerk or is there some sort of driver psychology going on where they unconsciously slow down or is there something, like wind resistance, that's slowing the car in the left lane? I realize that I will run into jerks, but driving jerks don't typically do things to slow themselves down, so I'm thinking it's happening for some other reason.