Lua has the following advantages over Lisp-the-language:

  - only one dialect (sometimes changes between major versions,
    but there aren't multiple dialects evolving in parallel).

  - infix notation is preferred by many programmers, and is easier
    to use for non-programmers.

  - the language is small (more like Scheme than Lisp)

The Lua and LuaJIT implementations have the following advantages over SBCL (you didn't say which Lisp, so I'm just picking what seems to be the most popular one):

  - extremely portable
  - extremely small
  - easy to sandbox
  - very good integration with existing C and C++