The second lane from the right is for people driving faster than people in the right lane.
The left lane is for people driving the maximum speed limit. People weaving in and out of the left lane so they can pass people who are driving at the maximum allowed speed are a problem.
Because instrumentation is imperfect, two drivers who believe they are driving at maximum allowed speed could be driving at different speeds. Ideally, there would be enough lanes for people to travel constantly in the second from the left lane at maximum speed limit, and to move into the left lane to pass somebody who's instruments have them traveling slightly slower. But traffic is never ideal, and extra lanes are very expensive. So people need to chill when the driver in front of them seems to be traveling 2mph below the max speed limit. On a 60 mile commute this won't make more than 2 minutes difference in your arrival time. Probably closer to 10 seconds.