May I ask what general area you are from where
John is underused? I am from Massachusetts, and as far as I can tell 2018 is the first time ever it was out of the top 10 (#13). I was born in the 90s and I went to school with many. And many of them went by
Jack as a nickname, whereas I've seen a lot of very surprised comments from people from other parts of the Anglosphere that
Jack could ever be a nickname for
John.
I do agree that it's handsome, though.