It is a perfectly defensible goal to have some or many pure functions within an imperative programming environment where state is persisted in variables outside of the library of pure functions. I don't think it is fair to equate pure functions with pure functional programming.

In a mixed model, you can have a mutable state but still have a large bank of trustable, testable, parallelizable behaviors defined in pure or deterministic functions with well defined contracts of input and output states.