"but I can't think of anything it does that most other programming languages don't do better."
What do you mean by that? Io is slow and does not have the extensive libraries that are present in other languages. However, as a pure prototype oo language, it is second to none.
Have a look at: https://github.com/mirage/ocaml-cohttp
You can of course also use cohttp directly but it's a little raw.