When is eye dominance useful?

LASIK and hunting: Eye dominance needs to be determined for eye surgeries such as lasik, and of course the dominant eye is used to focus when shooting.

Always: The brain, when both eyes are working well, establishes in early life one eye as the dominant eye - guiding the visual system and frequently providing the best vision. The brain will do this unless it does not need to (only one eye being sighted and the other low vision or blind). The brain perfers this dominance which is why it starts so early in life.