The MIN, MAX, and DELTA (or TIR) measurements are important for ensuring that the part you have made is precise enough to function properly. If you are building a part that will need to work as just one piece of a bigger mechanism, then you will need that part to be the correct shape with the correct surface structure. Using an indicator to measure the MIN, MAX, and then the corresponding TIR will help you to do this. For example, if you are building an axle that will be used in a bigger machine that produces parts for space shuttles, you need that axle to fit precisely where it needs to in the bigger machine. Additionally, you want to ensure that over time, the surface of that axle wears evenly rather than unevenly, as uneven wear might disrupt the functioning of the machine and the corresponding parts it produces.