This applies to many arts, as I have been looking at the kata list of many systems in the recent past.
I sometimes wonder why masters of the arts feel the need to create additional forms. Not that I don't understand the desire to add to the art, to add your own lasting impression. But why is it always the lower side of the curriculum - it is always for the most junior students.
Now, I can understand why this would be necessary, at least for the first few generations. After all, assuming that you learn from a battle hardened warrior, he is not necessarily a born teacher, nor does he necessarily have the basics organized in a way that is easiest to learn, or in escalating terms of difficulty. So as a student of such a teacher, you set about organizing what you have learned. Perhaps you take some of the easiest things and organize them towards the start of one of your new student's learning career. And then either you, or one of your students, starting adding forms to help in this. Perhaps, like Anko Itosu, you create forms for children starting to learn your system and arts.
But cut forward to modern day. Why create a new style, or keeping what you were taught, you decide to add to it. But you are not adding something missing from the system - a weapon, or technique, or skill set, or whatever you find isn't included. You add more to the lower end.
Is this done because the students are dumber than in your day? Or perhaps it is just because you start children younger and you need something even a 5 year old can do? If this is all just for children, why bother having adults learn this curriculum - it becomes irrelevant once you have the higher levels. For that matter, why bother having it for any one older than 12 - at that age they can easily begin learning the true art, and 5+ years of training puts then in a good position to prepare for blackbelt.
Or is it because you believe you need to add to the system, but you don't know or believe that you are capable of adding something more comprehensive? Or is it because you haven't learned anything so you don't know what to add? Or is it because you want to believe in your own image as a great and powerful martial artist?
I am not accusing anyone - this is all just a thought exercise on my part. It is relevant as I wonder if I will ever make a contribution to my own art. Something truly non-trivial. Something that adds depth or at least something not yet included natively. I could go and learn Indian stick fighting or Filipino dagger techniques, but would they mesh with what I know and do? The how of getting from point A to point B is interesting as a thought exercise.
Food for thought, as the saying goes.