For many, Lua is primarily known as the Roblox language. Pretty impressive that it's the language of use in a game (/set of games) with 380 million monthly active players - currently the most popular in the world.
Lapis is very cool, but I really struggle with a lack of examples and pre-built solutions for some things.
Leafo's itch.io is built with it and I maintain snap.berkeley.edu. A great tool, but I'm also many times more productive in Rails. (It's an unfair comparison, to be sure!) and Openresty + Lapis is quite performant and low overhead which is great.
I see your point. I've just craved a rails-like experience in Lua for a while and don't believe there's anything out there yet built on Lua that can match with the big boys (rails, .NET, etc.)