It helps if you realize that there are no arrays in Lua. Instead, everything is an optimized hash map that can be indexed by any value of any type. A single table can have some elements indexed by integers, others indexed by strings, function pointers (useful for a table of debug hooks), etc.
The few convenient things that expect tables to be indexed using integers starting at 1 are the # operator to get the number of elements, and the ipairs function, used in the common idiom “for index, value in ipairs(t) do . . . end”.
Normally education or human oriented languages start arrays at 1 (Smalltalk, Cobol, Lua, APL, Wolfram, etc) while hardware oriented languages start arrays at 0 (C and friends, Oberon, Forth, Scheme and so on). Human oriented languages that have to play nice with C also tend to use 0. As do Python and Basic, which contradicts my rule.
Probably the number one reason not to start arrays at 0 in an educational language is that having the last element of an array of size 10 have an index of 9 causes quite a bit of confusion.
I have to admit that this was one reason why it took me so long to start a project with Lua. Now that I've had some exposure to the language, I can say that it's not as bad as it seems, but it's also not "nothing". I frequently have to think about indices to avoid making mistakes in Lua, while in zero-based language indexing is pretty much muscle memory.
