I didn't use real names but that's because I'm so terrible with faces that I'd keep forgetting people or getting their name wrong - so I figured that using names would make me look like more of an idiot!
Similarly, I appreciated it when those who I refereed regularly still made a clear point of calling me ref.
The other issue is, there are team I might ref 5 or 6 times in a season. If I'm calling all those players by name, and they're playing against a team I might see once or twice a season and don't know anybody, then IMO I'm no longer appearing impartial - it looks like I have a closer relationship with one team.
IT's like when you turn up to the field and see the ref being all chummy with one of the teams. Just something to avoid.