I pinch to steer growth in "trees in training". This includes steering the growth of scaffolds by keeping the growing tip headed in a straight line from the trunk and from from being dominated by a lateral. A straight branch is an efficient one. A well trained tree doesn't have zigzagging scaffolds.
The same thing goes with even younger trees to maintain dominance of a central leader. When a sapling tree is cut down in height several buds form at the cut- pinching is the most efficient way to grow the trunk back up with a straight spine.
Then there is pinching of shoots on espaliers, or similarly trained trees, where you pinch back annual shoots several times during spring and early summer to force the formation of a fruit spur.