There's no reason? Are you sure about this?

I think you mean there could theoretically be an interpreted Rust, but I don't think anyone has ever made a prototype of a Rust interpreter.

The closest is probably rust-analyzer (the official language server), that maintains internal state and reacts to changes you make, but it doesn't create an executable artifact.

The other is probably the Cranelift Backend (https://github.com/rust-lang/rustc_codegen_cranelift), which can produce debug builds quickly.