Rust is a system programming language. If I have a new idea for an allocator they want me to write the experimental version in rust. If you never write an allocator and other such tricks you don't need unsafe - you could use one of the other languages. Java doesn't have unsafe, but you cannot write a custom allocator in java (well you can, but it will by a manual process to use it - you have to drop back to C if you want java to use your custom allocator by default)