Let's take another example. Consider structs as tagged tables with a metatable key that distinguishes it from ordinary tables. You can implement inheritance as chained __index closures for parent tables or simply chained tables. Or you can use the struct as is by defining a global table and creating a simple lookup. Theoretically the lookup will work faster because you can store the hierarchy as an list, run a simple index() to get the needed parent and call the method in the associated table. This is much faster than going to multiple chained tables thus slowing down lookup.

Another example is python iterators which requires a separate instance with __next__ method. It is not generic because now you can create n instances for n dicts just to use it in for syntax. Whereas in lua it is a simple closure returning the next value until nil