This law really has nothing to do with any limitations on AP. Left lane travel is for passing regardless of your speed.
If you're going 60 in a 65 and you move into the left lane to pass someone going 55 you're in the right. Just because someone comes behind you going 65 or more doesn't make you susceptible to getting a ticket.
Most intercity highways are 2 lanes in each direction and most states have different speed limits for semis, vehicles with trailers, and passenger cars. Because of the lower speed limit for trucks, most of them are in the slow lane. Anyone trying to drive a passenger car at the speed limit in that lane is going to end up driving the truck speed limit most of the time because they can't get into the left lane to pass the trucks. On the rare occasion there isn't much traffic, it might be possible, but that's a rare occurrence in my experience.
The way things shake out on those highways is the right lane is for trucks and the slow pokes and the left lane is for everyone else. If you are unwilling to do the speed everyone else in the left lane wants to do, which is usually around 10 mph over the car speed limit, you are going to be blocking traffic.
Someone who is sticking to the speed limit and going in and out of the right hand lane, only using the left for passing is likely going to cause an accident when they pull into the left to pass a truck doing 65 and someone doing 80 is already in the lane.
Speeding in and of itself causes few accidents. Especially only a few miles an hour over the speed limit. When speed is a factor in an accident it's when somebody does something or something happens beyond just speeding. The faster you are going when a blown tire happens, usually the worse things are, but most people drive their entire lives without having a blow out. I've seen it happen twice, one in a car and another time I saw a semi tire blow. The car tire blow out totaled the car, but it didn't appear anyone was hurt. The truck just kept going.
Other things can happen beyond just a blow out that can cause a single car accident. People hit debris, animals, or have other mechanical problems that can cause accidents. Speeding at these times can make the accident worse.
The other situation where speed can be a contributing factor in an accident is when either the speeding car is maneuvering, or another car maneuvers into the speeding car's path. People who frequently change lanes are putting themselves and others at a lot more risk than people who are just cruising along in one lane, even if they are a bit over the speed limit. I have seen kids weaving around cars on the freeway on several occasions and many times they have almost caused accidents as they slit into narrow gaps and cut things very close.
On a clear day, dry pavement, traffic load within the limits of the road, etc. it's rare for moderate speeding to contribute to accidents. Especially if everyone is traveling around the same speed.
