I think Python has pretty good marketing, actually. Whoever does their webpage does a great job of making it look mature, stable, widespread, and approachable, IMHO. (If you want to see a language which is actually really cool, but historically hasn't done a good job of marketing itself, look at OCaml. Maybe it's had better marketing in French, though.)

Also, Lua is in a bit of a unique situation, because probably half the people using it (give or take) are using it inside of an existing project, which would provide most of the libraries they need. Also, the Lua team has intentionally made it easy to fork local dialects of the language, which in many cases are probably too nuanced to be of general use. (It's MIT licensed, so there's no requirement to contribute back.)