I wasn't trying to argue that this was the only or even the best way of doing it, just why it's advantageous that you separate runtime and compile time function

I wasn't trying to argue that this was the only or even the best way of doing it, just why it's advantageous that you separate runtime and compile time functions, especially in languages with eager evaluation. The advantage of macros is just that they are simple to understand and use (for most you basically just have to understand tree data types, or just cons, especially for CL style macros), to implement (since every (?) language already have an AST representation, and particularly powerful in Lisp for obvious reasons) and the language doesn't even really have to support them in their normal syntax (fully separating runtime programming syntax and compile time programming syntax if they want). And for that they give a lot of power by allowing easy language extensions, syntactic sugar and powerful optimizations.