From Lua's Wiki: Lua is crap!
"Lua is a tiny and simple language, partly because it does not try to do what C is already good for, such as sheer performance, low-level operations, or interface with third-party software. Lua relies on C for those tasks. What Lua does offer is what C is not good for: a good distance from the hardware, dynamic structures, no redundancies, ease of testing and debugging. For that, Lua has a safe environment, automatic memory management, and great facility to handle strings and other kinds of data with dynamic size."
In this modern age, battery life is just as important as absolute performance.