It really isn't a pronoun, but goes into the implicit versus explicit thing. If your pronouns are "He/Him" you want to be called "Man", implicitly. If I don't say "Dude", explicitly, how are they to know?... Plus, I've met several people who chafe at being called "Dude", and I prefer it TBH. "Hey, dude" or "Dude's got good coding practices" are perfectly fine by me, but I'm also in my 40's and it shows =/