Earlier quoted context omitted.
I don't see why it is redundant. There is no reason to assume that the quoted sentence ends the quoting sentence. Imagine this being the last thing you see on a page. Without turning the page, there would be no way of knowing whether the quoting sentence is complete. But these things are just conventions. It's futile to demand any kind of logic or consistency.
It's not the only element of style that may seem illogical, there are many more. Off the top of my head: * Nested parentheses. (In theory, you could use any level needed (provided that they make sense), but in practice, they're scoffed at.) It is similar with quotes, for the same reasons: limited readability - although here you can at least juggle with single, double and French quotes, depending on the language and s…
Any level of nested parenthesis is fine (is what I think at least (as someone who's written a bit of Lisp of Lisp (or Racket and Clojure specifically) (because you get kinda used to it (when in a way they just become invisible (or unnoticeable))))). But nested quotations is also an issue with backtick (`) when doing command substitution in the shell, and we have to resort to $() to fix it. There's not really a $()-like syntax for written English though.