Rust does eat its own dogfood with regard to macros, and over time has steadily replaced former language-level features like `log` and `panic` with macros. Syntactic distinction is a philosophical choice in service of making costs more explicit (and while it's true that functions can hide behavior, overuse of macros can trigger enormous code bloat, such as the `regex!` macro which compiles your regex into a state machine).

(There are also valid technical reasons for requiring syntactic distinction, as the sheer flexibility of Rust's macros in their ability to create new syntax run the risk of making it a nightmare to parse if you remove the unambiguous ability of the compiler to drop into macro-parsing mode. These challenges aren't insurmountable, just very hairy.)