You'd have to make special case syntax for it and it would just feel bolted on to the language. Plus, tuples lose their usefulness if you have to declare its type to pass it between methods.

I think it could be OK even without return type inference on methods. Imagine you could type this:

  (int, bool) TryParse(string str) {
     // do stuff
     return (num, success);
  }

That would be clean enough.