Worth pointing out for anyone who does not know, NLTK was started by the linguist Stephen Bird, and over the years had significant work contributed by graduate students... much of this was happening in an academic setting and funded by grants.
Far as I know there are not many academics using Rust... unless they are computer science academics the typical target of PL is something perceived as "easy" to pick up (R, Python, Matlab, Julia).
In fact, the only academic i know working on NLP/Computational Linguistics and rust is (https://elaml.danieldk.eu/schedule/) @danieldk