- it is useful to linguists. (Modern linguistics borrows terms like sandhi and bahuvrihi for example.)

- it is acceptable to language users. Poets have continued to compose in the same language, without finding the formalization artificial.

- it is interesting even as an achievement of the human mind/culture.

A somewhat trivial example, but possibly of interest to the HN audience: the grammar needs to refer to various sets of sounds (like "nasal consonants", "short vowels", "aspirated stops" and so on). To compactly encode these sets, it adopts a curious ordering of the sounds, so that each required set can be represented as a certain substring of that sequence.

It turns out that this ordering can be shown to be optimal: see e.g.

- Economy and the Construction of the Śivasūtras by Paul Kiparsky, Stanford University http://www.stanford.edu/~kiparsky/Papers/siva-t.pdf

- A Mathematical Analysis of Pāṇini’s Śiva sūtras, by Wiebke Petersen, University of Düsseldorf http://user.phil-fak.uni-duesseldorf.de/~petersen/paper/pete...