Having used Lua a fair bit in the past year (in order to write custom plugins for Kong), the main draw (and in some cases, drawback) for me with Lua is its integration of coroutines. Draw as it makes writing event-driven code dead simple, with coroutines managed behind the scenes as you write code serially. Drawback as if you pull in the wrong library, one that does something in a blocking fashion (such as with a c module that doesn’t “get” Lua), you can get into some trouble.

In terms of syntax it’s basically JavaScript with stupid array indexing, which is enough to turn people off I’m sure.