Some people just like to have an accurate speedometer. I know I wish MINE were in all my vehicles.
You DO realize your speedometer "accuracy" will change as the tire wears...particularly with round profile MC tires. An old tire will be what....1/2 to 3/4 inch less tall than a new one...and have a smaller circumference...so it will travel less distance with each rotation...and make more revolutions in any given distance...making a change in speedo accuracy of approximately 3% over the life of the tire.
So whatever degree of speedo accuracy you have with a new tire it will be less accurate with a worn tire. True to some extent with any vehicle.
I'm just sayin'....