I feel like this might be something to prevent infamy from being spread to someone with a similar name, but also because having three names can also make "naming" them feel more serious. Like when you are a kid and you are in trouble with your mom and they use your full name to establish how you are in a lot of trouble instead of just a little trouble.
I feel like this might be something to prevent infamy from being spread to someone with a similar name
It's almost always this, serial killers usually get the same treatment. I think it was especially more important in years past when a full name was more often used to identify a person
Jerry: But lone gunmen assassins, they always have three names. John Wilkes Booth, Lee Harvey Oswald, Mark David Chapman...
Alice : John Hinckley. He shot Reagan. He only has two names.
Jerry : Yeah, but he only just shot Reagan. Reagan didn't die. If Reagan had died, I'm pretty sure we probably would all know what John Hinckley's middle name was.