You keep undoing this edit on the Corral page, once even citing that your dad's tractor uses the imagery as a unit of speed.
But have you not considered that the measurement itself is used because of the aesop's fable? Tortoises and hare landspeeds are vastly different and are two completely unrelated animals, so why use them at all? Why would a tortoise and a rabbit/hare icon be used if not for the popular fable everyone knows about?
just adding to this, had it been solely for speed literally any comparison with animals, or even just colours, could be done, yet its consistently a tortoise and a hare in 99.99% of cases (seen once on a kids toy where it was a snail and a hare). these sorta things aren't just done for the hell of it, they themselves have a history. a snail and a cat would serve the same purpose had it just been a speed thing, yet the tortoise and the hare were chosen. many things in today's society trace their roots back to some small tales, myths, or events such as this. that does not mean that wasn't the origin of the concept just because it is widely spread in the modern day.
if you ever have some free time, its actually surprising to look into where some pop culture aspects draw their roots from.