Why do people sign their names with only their initials?
There are many reasons not to include a full first name.


You don't like or identify by your first name.
The journal format demands it.
You are trans-gender and have changed your first name, but not the initial or your surname.
You are a minority in your field and hiding your first name means hiding clues to your minority status and possibly increasing the odds of your work being taken more seriously. (Mostly, hopefully, this reason is now outdated.)