When you don't, you'd likely have an Maybe<string> for a username that would be a "string?" in C#. It's the same thing (more or less). For your optional type you still need some form of pattern matching to figure out whether you have it or not.

You can't banish the "absence of value" from any programming language. That wouldn't be a useful language. You can stop confusing "a string but perhaps not" as a single type "string" as C# did in the past though.