The borrow/lifetime system never changes the behavior of any program, the only thing it can do is to disallow some programs from compiling. This is not how the rest of the type system works.

This means that it's possible to write a compiler that correctly compiles all correct rust programs without having a lifetime system at all. It also means that having the lifetime system in makes writing programs more complicated, but it makes reading them, and understanding what a program does, easier.