“In Ocarina of Time, the Kokiri are not visible from more than fifteen steps away. This is due to the Nintendo 64’s limitations, as it was difficult to display the Kokiri and the structures in the Kokiri Forest all at once, so each Kokiri was paired with a Fairy to help locate them. When Link approaches them, their owners appear.”
Why did the Deku tree give every Kokiri a fairy? To improve performance on the N64. Nintendo’s harmony between development and design strikes again.