That's exactly the challenge though: "any good crypto library" - there is a long history of meaningful security breached (like stolen crypto tokens) due to bugs in an upstream library, especially when using things like embedded code, alternative operating systems, newer programming languages, etc.
The value of the iterated hashing method is that it is dead simple and has little dependency on potentially buggy upstream code; it works even in very lightweight environments designed by engineers with no experience in security.
The value of the iterated hashing method is that it is dead simple and has little dependency on potentially buggy upstream code; it works even in very lightweight environments designed by engineers with no experience in security.