One of the languages that originally featured REPL, Lisp, was always compiled, both to machine code or byte code. Ditto smalltalk. I am not even sure which "traditional" languages you are talking about.
When I mentioned state, I did not mean testing. Sure, a properly designed system will have all it's computaional parts abstracted in a functional way so it will be trivially tested compiled or not. However, REPL is incredibly useful during the development process when the abstractions required are not yet clear, so it allows one to easily explore design possibilities without committing signficant effort of implementing a correct compilable module.
When I mentioned state, I did not mean testing. Sure, a properly designed system will have all it's computaional parts abstracted in a functional way so it will be trivially tested compiled or not. However, REPL is incredibly useful during the development process when the abstractions required are not yet clear, so it allows one to easily explore design possibilities without committing signficant effort of implementing a correct compilable module.