Here is a good quote from Kenwa Mabuni on why kata needs to be a part of training, but also why it should not be the whole of training:
“Therefore, kata must be practiced properly, with a good understanding of their bunkai meaning. There may be those who neglect the practice of kata, thinking that it is sufficient to just practice two-person drills that has been created based on their understanding of the kata, but that will never lead to true advancement. The reason why is that the ways of attacking and defending have innumerable variations. To create two-person drills containing all of the techniques including each and every one of their variations is impossible. However, if one practices kata correctly, it will serve as a foundation for performing - when a crucial time comes - any of the infinite number of variations. However, even if you practice the karate kata as you should, if that is all that you do, if you do not train sufficiently in other areas, then you will not develop sufficient skills. If you do not also use other training methods to strengthen and quicken your hands and feet, as well as to ensure the sufficient study of things like body-shifting and distancing, you will be inadequately prepared when the need arises to call on your skills.” – Kenwa Mabuni, “Practice Karate Correctly”
I like this a lot and it is very much in line with my own thinking on kata. We need to understand bunkai; we need to know that the kata gives us an example of combative principle – not just a specific technique – and all other ways in which that principle can be exploited must also be part of study; and that kata needs to be part of an overall holistic training program. Great quote!
All the best,