It's really really hard to get things right with pure functions. Haskell struggled with this for decades. You can't expect to be able to import this in some ran

It's really really hard to get things right with pure functions. Haskell struggled with this for decades. You can't expect to be able to import this in some random language and just make it work. So random languages just pick what they like (lambda expressions, weaker forms of algebraic data types, sometimes the complete typeclass concept, various forms of Monads from "unnecessarily specialized because whoever picked it didn't understand it" to "properly done"0. And while having pure functions certainly forces you to get things right, you don't need to do this when copying ideas. And there are functional languages (some very old, like Lisp) that never had pure functions in the first places.