> why would we use anything but actual natural language?

Because natural language is not a good tool to describe computational processes.

Which one would you rather write:

(a) p(x) = x^2 + 5x + 4

(b) Let us consider the object in the ring of univariate polynomials with complex coefficients defined by the square of the variable, plus five times the variable plus four.

Every scientific discipline moves away from natural language as soon as possible. Low-code, no-code and the likes have been a dismal failure precisely for this reason. Why would I move back to natural language if I can effectively express my problem in a formal language that I can manipulate at-will?