Really? I have never known a person who has a name that easily lends itself to a nickname who doesn't use the nickname. I've known two Benjamins, both called Ben, multiple Christophers who were all called Chris, two Rebeccas who were both Becky, Alexandras who were always called Alex, my sister Patricia is always called Patty, my sister Pamela is always called Pam, every single Joshua I've known has been called Josh and never Joshua, every single William, and there have been a lot I've known, was Bill, with the exception of my son, who is called Will. Never known a Richard who wasn't Rick. And my experience has been that these people get pissed off when you call them by their full names. It's a habit I have of occasionally calling a person by his or her full name, and when I do, invariably I hear, "Don't call me that", to the point that I've tried to break myself of the habit. Then there are people whose full names are no longer than two syllables and don't really need a nickname, so they don't have one, but I'm speaking of longer names that have common nicknames.
I did know a girl in high school who was named Cynthia and wanted to be called Cynthia, but I also recall that she had to constantly correct people who automatically called her Cindy. The other two Cynthias I've known, one a good friend, were always called Cindy.
Guess that's why I tend to be in the "nicknames are unavoidable" camp.