Driving would be a lot better, easier and safer if people were courteous of the people around them. Too many people (some represented in this thread) that seem to enjoy driving against the norms, just to irritate those people around them. They insist on driving slow in the left lane, just because they think they can. They enjoy seeing people behind them that are irritated with their selfish decision.
When I tow I stick to the middle or right lanes on the highway, as I tow at about 67 mph. There is no raeson for me to be to the left of the highway at those speeds, and it causes issues behind me if I were to try. I will never understand the willful disregard for other people.
Bottom line... if you aren't going faster than the vehicle to the right of you then you should move over one lane to the right. If you still aren't going faster than the vehicle to the right of you, keep moving one lane to the right until you have found the appropriate lane.
Cars driving slowly in the left lane are an obstruction. Most states have, and enforce, laws for cars driving either below the speed limit OR below the reasonable flow of traffic. The reasonable flow of traffic can be faster than the speed limit.