The fact that a tool is rarely used or rarely even needed is only one factor in determining whether it should be made available.
Another factor is how necessary such a tool is when those situations do come up.
Not proving necessary tools for a task means the task can't be performed. With current D&D math, tools are required to create novel monsters that fit the math. Not providing them means novel monsters can't be created. Deciding not to provide them means deciding novel monsters will not be made.
Is that a good decision for the D&D publishers to be making?
Now, a good compromise would be releasing a tool outside the DMG. I'm not opposed to digital tools, but I'd prefer (instead or also) a written tool where I could see everything it's doing and not have to extract it from a possibly opaque digital implementation.
Got an idea for what I could have reskinned to create my
yuki-on-na? (Post #6)
EDIT: I want to clarify that while my opposition to WotC decisions is based on principle, it is also a practical matter. I created the yuki-on-na conversion because I need it for an adventure I'm making. I used it in the post because the timing aligned. If this were 2030 and I only had the 2024 materials, I would have been out of luck.