Sometimes, safety is faster than unsafety, because it lets you achieve algorithmic speedups in a more maintainable way. For example, Stylo, the new parallel rendering engine in Firefox, was attempted in C++ a few times. It failed each time. However, the project succeeded in Rust instead, and is much faster.

Additionally, the goal of unsafe is not to throw away all safety; it's to prove to the compiler something that you know, but it does not know. This means that you can contain the unsafety, and still gain the benefits as a user. The goal is to isolate and contain it, making it easier to write correctly.