Real machines and reality aren't built out of safe primitives. Safe constructs have to be built out of unsafe components. That's just how computers work.
Sure, that's why safe languages forbid users to use unsafe things.
"C programmers think memory management is too important to be left to the computer. Lisp programmers think memory management is too important to be left to the user."
Ellis and Stroustrup, The Annotated C++ Reference Manual.
You need a systems programming language to write safe systems. That's what Rust is. Maybe there's room for a higher-level 100% safe language. Rust would be a good language to write it in.
In the mean time, in the messy world of writing software today, one does frequently enough come across the need for new safety primitives. Things that are provably correct but which the type system of your language does not support. In these instances, unsafe lets you lower down into systems code to build and safely wrap these new components.
Yes, Rust is a good systems programming language. Just not safe. Safer than most others, yes. Good enough, yes.
But there exist safe systems programming languages. Safe systems were done in these languages. Just nobody cared, so they died or have no market share.
Do I have to do osdev language research for you now? I'm certainly missing some, but out of my head: Mesa/Cedar, Concurrent Pascal, Smalltalk, Lisp, ADA, C#/M# for Midori/Singularity, Oberon, ...