It didn't mention the speed limit; it mentioned the flow of traffic:
"As used in this section a slow moving vehicle is one which is proceeding at a rate of speed less than the normal flow of traffic at the particular time and place."
I'm just saying; when even ONE person is lined up behind me, I assume they have a medical emergency, or are in some other huge hurry, or just like to drive faster. Why would I want a monster truck (or any other car) 6" off my bumper? If I can let them go by, they keep speeding on their merry way, and now they are "running interference" for me (cops will pull them over before me, perhaps).
It isn't my business if they want to speed or not; I'm not the police. It's like a bike path; if I had people, even one, lined up behind me, trying to say "on your left" (which is very difficult to say in a car, all you can do is hint that you'd like to pass), I wouldn't ignore them, I'd try to courteously let them go by me. Why, in cars, do people want to have people behind them instead of trying to get them to go by? #foreverconfused