Yes, but it also states that on a 2 lane road, you can exceed the speed limit for as long as necessary to pass on the left if the car you are passing is driving below the legal limit and you are at a point where it is legal to pass.
An example is that if the speed limit is 55mph, it would generally be allowable to speed up to 60 to pass a farm vehicle traveling at 45mph on a 2 lane road provided that you're at a location where passing is allowed (clear line of sight, and the center line would be dotted instead of solid, no oncoming vehicles that would have to brake, etc.).
The second paragraph of that act does note that some roads may have minimum speed limits posted which you're not allowed to go slower than provided the road conditions are normal.
But I think the real reason is that people would be very, very grumpy about that law and regulators need to pick their battles.