The question is far too broad, and contextual. You're never going to get an answer to that question. Sometimes, the rules add more optimization potential. (lik

The question is far too broad, and contextual. You're never going to get an answer to that question. Sometimes, the rules add more optimization potential. (like how restrict technically exists in C but is on every (okay almost every) reference in Rust) Sometimes, the rules let you be more confident that a trickier and faster design will be maintainable over time, so even if it is possible without these rules, you may not be able to do that in practice. (Stylo) Sometimes, they may result in slower things. Maybe while you could use Rust's type system to help you with a design, it's too tough for you, or simply not worth the effort, so you make a copy instead of using a reference. Maybe the compiler isn't fantastic at compiling away an abstraction, and you end up with slower code than you otherwise would. And that's before you get into complexities like "I see Rc<RefCell<T>> all the time in Rust code" "that doesn't make sense, I never see that pattern in code".