Why have we not seen an effort to build a solid ecosystem around it the way node has with JS? Lua with equivalent libraries to Python/Ruby/Javascript/PHP would be superior to any of them.
One thing that I think people get confused about Lua is that its simultaneously a VM, a language, and a very minimal framework, around which many, many things can be glommed. The glomming of those things is so flexible and versatile that - indeed perhaps we see too much diversity in the Lua appliance world, for there to be any common centralized traction around promoting it, as has happened with node.
If you want to see how Lua really has a solid ecosystem, then you have to look for projects that have embedded the VM and are using it as the basis for their application run loop. And indeed, there are plenty of projects out there doing this, that it can't really be said Lua doesn't have traction; it just doesn't attract as much hype. Lua has plenty of libraries; its just that the "FFI all the things!" approach means that you can, pretty much, indeed FFI all the things. No standards committee required!
Lua really ought to be considered JS done right and Eich should really have been given enough time to bring scheme to the browser (syntax could have been negotiable). Another interesting project is Typed Racket http://docs.racket-lang.org/ts-guide/index.html?q=typed and Guile http://wingolog.org if this sort of things interests you.
[4] http://www.keplerproject.org/
[5] http://luvit.io/
3. http://www.techempower.com/benchmarks/#section=data-r7&hw=i7...
Typed Lua says it only works with Lua >= 5.2. LuaJIT runs a language that is somewhere between Lua 5.1 and Lua 5.2, so it's not clear whether it will work with Typed Lua. The 5.2 requirement may just be to run tlc (and not the code it outputs), in which case you could run LuaJIT + Typed Lua + nice C libraries.
Language adoption is a very social thing though. Maybe if Rails was a Lua framework we would be wondering why Ruby never made it big.
Lua is embedded in things like Redis, and is often uses as an extension/configuration language for small projects.
I based my mail client(http://lumail.org/) around Lua as a configuration language because I kept getting annoyed by the almost-configuration-language used in mutt.
Actually writing applications in Lua is also possible, for example the chat/Jabber server Prosody.
Note though it does lack some syntactical sugar, and arguments not passed are silently 'nil', so it is not strictly superior.
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The complete ecosystem being referred to is all of the libraries available in node's package manager (npm).
If lua had an awesome built-in package manager like npm, it would be possible for the lua community to develop a library ecosystem that competes with node's.