SLIME for Lisp exists since a long time. It has a server component.
From what SLIME provides, one can see that the functionality used for interactive Lisp programming is different what one would use for many other languages. One is not communicating with a "language server", but with the live running application and its embedded development tools. For a Lisp programmer it is interesting where a CLASS is in the source code, but it is slighty more interesting to interact with the live class object (a metaclass object). CLOS (the Common Lisp Object System) was designed for interactive programming. That's also why it is said to be a 'system' and not only a language.
From what SLIME provides, one can see that the functionality used for interactive Lisp programming is different what one would use for many other languages. One is not communicating with a "language server", but with the live running application and its embedded development tools. For a Lisp programmer it is interesting where a CLASS is in the source code, but it is slighty more interesting to interact with the live class object (a metaclass object). CLOS (the Common Lisp Object System) was designed for interactive programming. That's also why it is said to be a 'system' and not only a language.