Many people have relatively common names; middle names help to differentiate. If I say Michael Fox you probably have no idea who I'm talking about. If i say Michael J. Fox you know who I mean. 
Usually, when Hollywood actors first get started and few know who they are, they are cited merely by first and last name. I remember when Samuel L. Jackson was simply Sam Jackson in the film, "Strictly Business", starring Tommy Davidson, Halle Berry, and, Joseph C. Phillips.
Another one that comes to mind is Wendy Robinson, now known as Wendy Racquel Robinson from "The Steve Harvey Show" and "The Game".