Question about how rust async/await works internal?

as i read the Rust async-book(https://rust-lang.github.io/async-book/), it's a poll based model, it's generated statemachine like i pre learned C# async/await works, in C#, it rely on awaiter's complete callback to move to next state, why rust rely on a waker to tell executor to poll again, is this pattern better ? why ? how many async model used in async/await world?