> But code is just a spec as far as, say, a C compiler is concerned. The compiler is free to implement the assembly however it likes.

Not at all. Code is formal, and going from C to assembly os deterministic. While the rules may be complex, they are still rules, and the compiler can’t stray away from them.

Writing C code is easier than writing assembly because it’s an easier notation for thinking. It’s like when hammering a nail. Doing it with a rock is hard. But using a hammer is better. You’re still hitting the nail with a hard surface, but the handle, which is more suitable for a human hand, makes the process easier.

So programming languages are not about the machine performance, they are about easier reasoning. And good programmers can get you to a level above that with proper abstraction and architecture, and give you concepts that directly map to the problem space (Gui frameworks instead of directly rendering to a framebuffer, OS syscall instead of messing with hardware,…).