I've been using Java since version 1.1 and I've seen features added that required a new version of the language spec to go through committee and get implemented before we got to use them where you could just add these features yourself at the top of any Lisp file and then immediately start using them. For example consider the try-with-resources [0] syntax sugar. So instead of thinking "I never actually ran into a need for them", think of new language features that you have started using: those are the kinds of things you could've added yourself.

Also look at any kind of code-gen tooling like parser generators or record specifications like Protocol Buffers as examples of what you could do within the language.

[0] https://docs.oracle.com/javase/tutorial/essential/exceptions...