you need to realize lua isnt targeted as a batteries included platform, its design philosophy is minimalist, not junk included but customize for your requirements. where lua absolutely excels is when paired with C (not C++) and not used as "scripting glue" but fully integrated and driving the system. it really appeals to minimalistic / keep it simple philosophy guys which isnt the web community.
lua is not a one stop shop and will never be, which probably why it flys under the radar so much - you cant stamp a powered by lua logo on it.
I think it's true you need to watch out for this 'gap' between a full blown, batteries-included language, and something really small. Tcl sort of fell into it when they grew the language and libraries to the point where it's less attractive as a small, embedded language, but never really got it together enough to ship it with all the goodies included, either, meaning you have to round up a bunch of external things to do much with it. It's not a 'happy medium'.
lua is not a one stop shop and will never be, which probably why it flys under the radar so much - you cant stamp a powered by lua logo on it.