Often they don't and it's kind of the point. You could go by Rich, Richie, Rick, Ricky, Dickie... if you choose to call yourself Dick, you know you're going to cause some amount of snickering and you're doing it on purpose.
Also I remember men called him Richard Feynman but a lot of women called him Dick. That's sending a different message.
I recall sitting in a seminar in Australia, conducted by an American man called Buck Rogers. I had a moment of disbelief when he introduced himself.
I later found out that he had legally changed his name to Buck Rogers to intentionally be noticed.