I don't like using words for things that should be represented by symbols. { and } are much faster to read, interpret, and write than "then", "end", "do", etc. Not to mention that they literally make sense by encapsulating the code, the words "then" and "end" have no relation to encapsulation.
I've worked with Lua. More than once. I've seen what it can do, I've seen how it does things, and I've decided I don't like it. It's not for any one reason (it's not just because ~= is used instead of != or it uses keywords instead of symbols) but as a collective language it's just not for me. I don't think it's really for anyone, to be honest. It's really old and better languages exist for every use case.
Lua is slower than JavaScript which is slower than C++. Benchmarks exist, people. It's not opinion.
edit: better benchmark