Natural language is natural because it's good for communicating with fellow humans. We have ways to express needs, wants, feelings, doubts, ideas etc. It is not at all "natural" to program a computer with the same language because those computers were not part of the development of the language.
Now, if we actually could develop a real natural language for programming that would be interesting. However, currently LLMs do not participate in natural language development. The development of the language is expected to have been done already prior to training.
Invented languages and codes are used everywhere. Chemical nomenclature, tyre sizes, mathematics. We could try to do that stuff in "natural" language, but it would be considered a serious regression. We develop these things because they empower us to think in ways that aren't "natural" and free our minds to focus on the problem at hand.