It seem to me that Lua usage reside primary in the game industry.
People who works in the game industry and people who works in web technologies rarely collide with each other.
People who works in the game industry and people who works in web technologies rarely collide with each other.
Perhaps the reason Lua isn't gaining ground in the web scene is because it's too exotic, however fair that might be. It has a foreign object model and a different syntax. Both of these combined might create the perception that it's difficult to learn.
I'm not sure though. For me, I've always been interested in Lua, but I've never picked it up because I never see any web apps made with it.
Spreading knowledge between game developers is easier, though. People move around between companies a lot, and your publisher's team of lawyers is less likely to be present at a conference talk than finding NDA violations by crawling the web.
That's obviously the case for games and their 3D / physics engines, but Lua is steadily gaining momentum in the embedded devices world, where CPUs are also pushed to the limits of their (lesser) capabilities.
Web developers have already put most of their high performance wizardry in their SQL engines, and already have standardized/comprehensive APIs to these databases; I don't think Lua would bring them much, and certainly not enough to compensate for the loss of Python's or Ruby's existing web-friendly libraries.
Of course, the same goes for any scripting language (I've worked with a proprietary script language at my last dev shop), but I like the fact that lua is light, minimalist, clear and a standard that others will know, but also very extensible. I'd definitely say the the small core and lack of huge external libraries is a good thing, when you're developing for fixed hardware like game consoles.