Lisp compilers came into existence relatively early after interpreter, because of performance. And early compilers and interpreters had important differences in semantics, what everyone today means by "lisp" was in that day the behavior of compiled code, not interpreted (ie. dynamic vs. lexical scoping). The real value of first implementations of scheme was that they had shown that same semantics as were implemented by lisp compilers could be implemented by reasonably fast interpreter. And today there is Newlisp which has impressive performance for interpreted implementation, because it implements similar semantics as early interpreted lisps.