"Necessary" might be a hard barrier to get over, but I can think of times when it might be nice. For instance in C# optional parameters must be at the end of the parameter list (that is all required parameters must come before any optional ones).
So for our highly used method we realize that there is actually a reasonable default for the first parameter (maybe because we notice tons of usages of that value). In order to change this from a required to an optional field, we must move it to the back of the list.
Without an automated and safe way to do this, I'm unlikely to make that refactoring, leaving us with a code base that is worse than it could be. Again, is it necessary? No, but if it is trivial my code will get better, if it isn't my code will stay worse.
So for our highly used method we realize that there is actually a reasonable default for the first parameter (maybe because we notice tons of usages of that value). In order to change this from a required to an optional field, we must move it to the back of the list.
Without an automated and safe way to do this, I'm unlikely to make that refactoring, leaving us with a code base that is worse than it could be. Again, is it necessary? No, but if it is trivial my code will get better, if it isn't my code will stay worse.