Because function arguments are evaluated before the function itself. In this case, that evaluation would fail because numbers do not implement IFn, and hence cannot be called.
Macro arguments are not evaluated, and so this works.
You could make it a function, and pass the arguments quoted, but it'd be more cumbersome.
Macro arguments are not evaluated, and so this works.
You could make it a function, and pass the arguments quoted, but it'd be more cumbersome.