I have a name that has a ton of intuitive nicknames (not like Alexander, Samantha, etc) but most people including myself go by and introduce by the full version, but I’m not against any nicknames.
A while back, I had a teacher who called me by a nickname since the first day of role call without asking me first. One of my friends nearly exclusively calls me by a shortened version of my name, and I’m used to it.
Do people do this to establish rapport? I’m fine with nicknames, but it’s interesting how I introduce by my full name, then it immediately gets shortened.