> This compilicates things more compared to functions returning Result<>.

Checking each Result in a large program is more complicated than having a runtime library handling memory limits properly.

> And you also avoid mental overhead of managing many allocations in your head

That's exactly what languages like Zig force you to do, compared to something like C++ or Rust.

> or using a language with borrow checking

borrow checking gives memory safety. It's also important to have.