Below is another insightful post from Kachina Parts, a student of Kojo-ryu Karate in Japan, which I have translated into English.
About the only unarmed martial arts that does kata is karate. (Although some martial arts also use it). When I was young, I didn’t like kata and didn’t understand what they meant. I only remembered them because it was part of the exam for promotion to the next kyu or dan. Also, there was no one who could clearly explain to me what kata meant. Now that I think about it, if karate didn’t have kata, it would be a (different) martial art, like kenpo (boxing), or kickboxing. As for kata, there are many kinds found all over the world, and their interpretation vary. Personally I don’t give much importance to their interpretation, as I can only use one or two of them. The flow of an entire kata, including turning, stances, cadence, as well as acquiring techniques are much more important.
A Karate style’s kata is a collection of techniques and is used to immerse the body in those techniques; it is not a dance. There are times when kata techniques come out spontaneously when doing kumite and it is only when you continue to do kata that you realize that. The importance of kata is understood through kumite, as kata corrects your stance and your techniques, etc.. The old way was to teach the order of a kata and then simply repeat it. Its purpose was to imprint techniques into one’s body.
It is likely that people didn’t understand this, became bored with them, and then began to focus on kumite. Kumite, however, is not connected to kata because most kumite is competition-based . It takes three years to do a kata 10,000 times, even if you do the same kata 10 times every day. (The pre-war masters had experience in other martial arts and were able to master Karate in three to five years). It is thought that they repeated a kata 10,000 times. How many people have done one kata 10,000 times nowadays? This is what I discovered after doing Naihanchi kata more than 10,000 times.