Well, really the default is passing trivial implicitly-copyable values like integers. You probably don't want to write a & every time you pass an i32 to a funct

Well, really the default is passing trivial implicitly-copyable values like integers. You probably don't want to write a & every time you pass an i32 to a function, so that sort of thing gets the default just-passing-bytes-around syntax from other C-like languages. For resources or generally things that require cleaning up when they disappear, that just extends into the transfer, logically a shallow copy with the original variable flagged as dead in the type system. The & symbol denotes a reference type, and it's an explicit thing in the type system and not just an annotation as part of the function call process. It can show up anywhere you'd write a type, things like `Option<&T>` or other types with `&T` fields aren't too uncommon, and `&&T` is also a type. I haven't really thought it through, I guess, but modifying a type `T` with a `&` to make it a pointer type `&T` seems to compose a lot better than making all types `T` implicitly pointers and requiring `&T` whenever you want the value inline and not behind a pointer indirection, whether in a local variable or as a field in a struct.