If your user name appeared to be a real first and last name (fictitious or not), your user name has been changed to just your first name. As of May 1, 2018 no full real names are allowed as user names.
It was removed because it was only being used by one, maybe two people. And considering it's been gone for nearly a year now, that alone shows how often it was used.
Every add-on, no matter how insignificant it might seem, has an impact on how the site performs. To have an add-on for one or two people does not make sense. It's a matter of the greater good. I don't anticipate it being added back.