It is useful to differentiate this, though. Consider a datatype of map with values of type T. The function to return value for a key returns None when the key is not in the map, but what if the key is in the map, but the actual value is None? IIRC Lisp has a workaround but it requires special code to handle maps that can have None as values.

As the other posters have said, it (automatically flattening the Maybe monad) is non-composable and should be considered a bad language design, like it was a bad idea to automatically flatten lists in Perl.