C.W. Nicol in "Moving Zen" has an interesting perspective on the development of kata through the ages:
“From the very beginning of history, skill with weapons has been passed down by ritual practice. When the prehistoric or primitive hunter returned to camp after an encounter with a wild animal or enemy, he could demonstrate his prowess better by performing than talking. He would dance, exaggerating and repeating his movements. Young warriors and boys copied the dances, developed them until they were set and ritualized. They were superb training, for in them the warrior could mimic and develop the style, speed and skill of a master…..I believe that when we practice kata, we are somehow touching the warrior ancestry of all humanity”
Likewise, during randori (free or open sparring) or ippon kumite (single-move sparring with counter), kata applications should be incorporated and practiced as much as possible.