title: Why Mutex was designed to need an Arc in Rust
body: <p>Why was <code>Mutex&lt;T&gt;</code> designed to need an <code>Arc&lt;T&gt;</code> if the only reason to use a <code>Mutex&lt;T&gt;</code> is for concurrent code, i.e. multiple threads? Wouldn't it be better to alias a <code>Mutex&lt;T&gt;</code> to an atomic reference in the first place? I'm using <a href="https://doc.rust-lang.org/book/ch16-03-shared-state.html" rel="noreferrer">https://doc.rust-lang.org/book/ch16-03-shared-state.html</a> as reference.</p>