There is nothing quite like taking away the pain of a child. Until you're a parent yourself, at which point there will be nothing quite like inflicting it upon them. (Emotional only, of course.)
Most doctors enter into the medical profession with glory at least a little bit on their minds. While their intentions may be generally pure and come from a good place, they also want to be admired, looked up to, and relied upon. For a pediatrician, your patients are literally looking up to you. It's a nice bonus.