As an example on many bikes if you torque the rear axle nut to spec listed in the service manual then many times that pressure is so great that it causes the wheel bearings to be compressed into the spacer and it causes parasitic drag which makes it harder to spin the wheel than it would be if the axle nut was tightened by feel to the point where it starts to slow down the rotation of the wheel then backed off slightly and all while working to accelerate wear/tear on your bearings. Like everything else in the world that can be considered a profession there is a right way, a wrong way and the real way of doing things. I don't care of you are a mechanic, a programmer or a lawyer there are always written procedures that are intentionally disregarded in the interest of getting things done in a more proficient manner.