Is it normal that i call men named john by their last names?

I've developed this habit because every other parent even today decided to name their sons John, Michael, or David. Those are the three most common names I hear. That's why I now call them by their last names or shortened versions of their last names to avoid confusing them with other guys with the same name.

For instance, I had two coworkers named John. One's name was John Fitzgerald while the other's name was John Kozlowski. I called them Fitz and Koz. If anyone has ever seen the movie Rambo, the guy's name is John Rambo. The same is true about the Jud Nelson character, Bender, from The Breakfast Club. His name was John Bender, but everyone called him Bender. Chuck Norris played a character named John Braddock who people also referred to by last name. Ozzy Osbourne's real name is John Michael Osbourne.

I do this with guys named David and Michael as well. I once knew a guy named David Sullivan, but I called him Sully and another David who was there Chap because his name was David Chapman. I even knew two guys named Michael Seaver and Michael Lewis. I called them Seave and Lewie. Fitz, Koz, Sully, Chap, Seave, and Lewie couldn't argue because they knew exactly who I was referring to.