Exactly: a programming language is either like Python (“batteries included”) or it is like C (“do it yourself”; although there is a large stdlib called libc). The first is good for a general scripting, the second one isn’t. Yes, no sense adding file functions to Lua embedded in WoW, but e.g. Neovim (and any other editor like vis) must develop their own stdlib. Thus, “we don’t like you to use Lua for anything smaller than a project large enough for you to develop your own stdlib”.