What you propose would have, among other things, broken the well established expectation of random access for strings, including for slicing, while leaving behind unclear semantics about what encoding was used. (If you read in data in a different encoding and aren't forced to do something about it before passing it to a system that expects UTF-8, that's a recipe for disaster.) It would also leave unclear semantics for cases where the underlying bytes aren't valid UTF-8 data (do you just fail on every operation? Fail on the ones that happen to encounter the invalid bytes?), which in turn is also problematic for command-line arguments.