Leafly said it best when they described the care that goes into hand-trimming:
Quality hand-trimmed cannabis is the most precisely trimmed cannabis on the market. Every bud gets a custom cut to ensure that the strain’s particular characteristics shine through, and this method also protects the precious trichomes that hold the terpenes and psychoactive properties of the plant.
Each strain has a different appearance and each should be trimmed in a particular way to bring out its qualities—valuable calyxes and unique bud structures should be protected and celebrated. Some strains can be fluffy or dense, tall or stout, fragile or sturdy, and each should be trimmed accordingly, using human judgement.