I simply don't see any reason not to use it .. for everything.
I've built games with it. I've built GUI's with it. I've built scientific analysis tools with it. I've used it as a total solution for previously-impossible embedded problems. I've used it for desktop applications and mobile apps. I've automated entire production lines with it. It has huge appeal as a general purpose software development ecosystem - but those who know how to do this, tend to keep it to themselves for some reason.
It can do everything.
There's just nothing I want to do with computers that I can't, legitimately do, with Lua - or its VM. Or, LuaJIT. Or, all of the above and a bit of luarocks built in. Throw some luastatic in while we're at it, bundle it all up as a .deb, and nobody needs to know a thing.
Its just so versatile. I hope someone builds an OS around it some day, making everything and anything the user wants to do, accessible through a Lua module, or some smart libffi wrappers around a handful of .so's, somewhere ..
In my retirement, I'll take antirez' LOAD81, turn it into a proper Lua editor, add integration with luarocks and luastatic and maybe a shit-tonne of IPFS, and then there won't be any need, ever again, to deal with anything else.