Accuracy and repeatability is the lifeblood of all CMMs. If they aren’t accurate, there’s no point in having them. However, the degree of accuracy required is dependent on the particular application. For manufacturing gas turbines and aircraft engines, a very high degree of accuracy is often required.
Now imagine that you want to walk in a perfectly straight line for a half-mile. And imagine that at the end of that walk, you find that you are ±2.5mm (one tenth of an inch) out. You’d be pretty pleased. In the world of golf, you’d also be pretty pleased if you scored a hole in one every time you teed off to a green 14 miles away!